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الحمد لله رب العالمين والصالة والسالم على خاتم
النبيين
Geometric Design ndash Basic Principles Safety for all users Functionality ndash the need for access and mobility Accessibility for people with disabilities ndash as a prerequisite to
access to employment recreation and healthcare Mutual support and compatibility between transportation
facilities and services and the adjacent land uses and associated activities they serve
Consistency with transportation plans and policies and environmental regulations that guide the community the region the province and the Federal government
Transportation facility design and operational requirements established by others
Input and participation from local constituents and the appropriate local regional and state reviewing agencies 1048708
Cost effectiveness ndash the value returned for the investments made in transportation
GEOMETRIC DESIGN ndash Course Heads
Cross-Section Elements Horizontal Alignment Vertical Alignment Intersections Interchanges helliphelliphelliphellip helliphelliphelliphellip
Horizontal Alignment Roadways must respect the existing and
developed environment through which they pass
As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints
Horizontal Alignment Alignment constraints typically include
Physical controls - topography watercourses geophysical conditions land use and man-made features
Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas
Economics - construction costs right-of-way costs utility impacts operating and maintenance costs
Safety - sight distance consistency of alignment human factor considerations
Highway classification and design policies - functional classification level of service design speed design standards
Introduction of curvilinear alignments is necessary when the designer encounters these constraints
Horizontal Alignment Blending with the nature terrain existing features
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Geometric Design ndash Basic Principles Safety for all users Functionality ndash the need for access and mobility Accessibility for people with disabilities ndash as a prerequisite to
access to employment recreation and healthcare Mutual support and compatibility between transportation
facilities and services and the adjacent land uses and associated activities they serve
Consistency with transportation plans and policies and environmental regulations that guide the community the region the province and the Federal government
Transportation facility design and operational requirements established by others
Input and participation from local constituents and the appropriate local regional and state reviewing agencies 1048708
Cost effectiveness ndash the value returned for the investments made in transportation
GEOMETRIC DESIGN ndash Course Heads
Cross-Section Elements Horizontal Alignment Vertical Alignment Intersections Interchanges helliphelliphelliphellip helliphelliphelliphellip
Horizontal Alignment Roadways must respect the existing and
developed environment through which they pass
As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints
Horizontal Alignment Alignment constraints typically include
Physical controls - topography watercourses geophysical conditions land use and man-made features
Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas
Economics - construction costs right-of-way costs utility impacts operating and maintenance costs
Safety - sight distance consistency of alignment human factor considerations
Highway classification and design policies - functional classification level of service design speed design standards
Introduction of curvilinear alignments is necessary when the designer encounters these constraints
Horizontal Alignment Blending with the nature terrain existing features
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
GEOMETRIC DESIGN ndash Course Heads
Cross-Section Elements Horizontal Alignment Vertical Alignment Intersections Interchanges helliphelliphelliphellip helliphelliphelliphellip
Horizontal Alignment Roadways must respect the existing and
developed environment through which they pass
As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints
Horizontal Alignment Alignment constraints typically include
Physical controls - topography watercourses geophysical conditions land use and man-made features
Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas
Economics - construction costs right-of-way costs utility impacts operating and maintenance costs
Safety - sight distance consistency of alignment human factor considerations
Highway classification and design policies - functional classification level of service design speed design standards
Introduction of curvilinear alignments is necessary when the designer encounters these constraints
Horizontal Alignment Blending with the nature terrain existing features
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Roadways must respect the existing and
developed environment through which they pass
As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints
Horizontal Alignment Alignment constraints typically include
Physical controls - topography watercourses geophysical conditions land use and man-made features
Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas
Economics - construction costs right-of-way costs utility impacts operating and maintenance costs
Safety - sight distance consistency of alignment human factor considerations
Highway classification and design policies - functional classification level of service design speed design standards
Introduction of curvilinear alignments is necessary when the designer encounters these constraints
Horizontal Alignment Blending with the nature terrain existing features
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Alignment constraints typically include
Physical controls - topography watercourses geophysical conditions land use and man-made features
Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas
Economics - construction costs right-of-way costs utility impacts operating and maintenance costs
Safety - sight distance consistency of alignment human factor considerations
Highway classification and design policies - functional classification level of service design speed design standards
Introduction of curvilinear alignments is necessary when the designer encounters these constraints
Horizontal Alignment Blending with the nature terrain existing features
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Blending with the nature terrain existing features
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Horizontal alignment deals with changes in the
plan view of the roadway
Steps
Locating Laying out Highway Design Elements
bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Locating Highway
First Step
Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures
To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Locating Highway
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Locating Highway
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Locating Highway
Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided
Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized
Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance
The number of curves should in general be kept to the minimum
The alignment should avoid abrupt changes turns
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Locating Highway
Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas
Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and
increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be
bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)
bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two
curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Locating Highway
Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry
If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Locating Highway
The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry
Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment Locating Highway
Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Alignment
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Practice Session
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
5 10 15 20 25 30 35 40 45
5
10
15
20
25
30
35
40
45
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
500
1000
1500
2000
2500
3000
3500
4000
4500
3-D Model
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
MURREE HILLS
SIMLY DAM
DTM of Murree Hills
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
-1 00 000 100 200 300 400 500 600 700 800 900 1000-100
000
100
200
300
400
500
600
700
800
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
0 50 100 150 200 250 300 3500
50
100
150
200
250
300
350
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
360
380
400
420
440
460
480
500
520
540
560
580
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
National Forest Boundary
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
1500
1770
1850
2000
2150
2300
2450
2600
2750
2900
3050
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Straight segments are called Tangents Horizontal curves help change from one
tangent to another
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Design Elements Curves
Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves
Which one to be used where and how
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Simple Circular
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Compound Curves
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Horizontal curves are circular to minimize
steering effort Curves need to be long enough to avoid unsafe
or uncomfortable conditions Additional features can help reduce the driving
effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly
transition from an infinite radius (a tangent) to the radius of the circular curve
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Rmin = ___V2______
15(e + f) Where Rmin is the minimum radius in feet
V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and
graphed in Green Book) and design speed
bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo
bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph
bull f decreases as speed increases (less tirepavement contact)
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Max e Controlled by 4 factors
bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be
influenced by high super elevation rates
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves Max e
bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads
bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice
bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or
on a highway
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curves
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance
Horizontal Curve Sight Distance