Post on 30-May-2018
transcript
8/9/2019 Highway Capacity Lecture 1&2
1/63
Learning Objectives
To define basic concepts relating to highwaycapacity analysis
To apply capacity and LOS analysis forfreeways(Chapter 7.1 ~ 7.3; HCM Ch23)
Dr. Rakesh Kumar, Assistant Professor, SVNIT
8/9/2019 Highway Capacity Lecture 1&2
2/63
Transportation Facilities
Uninterrupted-flow facilities
no fixed elements external to the traffic streamto interrupt flow
Freeways, multilane hwy, two-lane hwy Interrupted-flow facilities
have controlled and uncontrolled access pointsthat can interrupt flow
(un) signalized intersections, urban streets
Performance?
8/9/2019 Highway Capacity Lecture 1&2
3/63
Capacity Analysis
Procedures for estimating the traffic-carrying ability of segments or points ofa facility over a range of defined
operational conditions
Purposes
Assessing facility performance
Planning and designing improved facilities
8/9/2019 Highway Capacity Lecture 1&2
4/63
Capacity
maximum hourly rate at which persons orvehicles reasonably can be expected to traverse apoint or a uniform section of a lane or roadway
during a given time period under prevailingroadway, traffic, and control conditions
(HCM 2000)
8/9/2019 Highway Capacity Lecture 1&2
5/63
Capacity
maximum hourly rate at which persons orvehicles reasonably can be expected totraverse a point or a uniform section of a laneor roadway during a given time period underprevailing roadway, traffic, and controlconditions (HCM 2000)
Base conditions
good weather
good pavement conditions
users familiar with the facility
no impediments to traffic flow
8/9/2019 Highway Capacity Lecture 1&2
6/63
Level of Service (LOS)
A qualitative measure describingoperational conditions in a traffic streamand their perception by Users/motorists
Range A (best) through F (worst) Determined by measure of effectiveness
(MOE) such as speed and travel time,freedom to maneuver, traffic interruptions,
and comfort and convenience
8/9/2019 Highway Capacity Lecture 1&2
7/63
Level of Service (freeways)
LOS A LOS B LOS C
LOS D LOS E LOS F
8/9/2019 Highway Capacity Lecture 1&2
8/63
Service Flow Rates
Maximum flow rate attainable ateach level of service (except for LOSF) for a given facility
Define the flow boundaries betweenlevels of service
Hourly service flow rate is defined asfour times the peak 15-min volume
8/9/2019 Highway Capacity Lecture 1&2
9/63
Capacity Analysis forFreeways
Only for basic freeway segments
Where there are no interruptions to theflow of traffic
Outside the area of influence of freewayweaving areas and freeway ramp
junctions
8/9/2019 Highway Capacity Lecture 1&2
10/63
Capacity Analysis forFreeways
Base (ideal) conditions
Minimum lane widths of 12 ft
Minimum right-shoulder lateral clearance of 6 ft
Minimum median lateral clearance of 2 ft 100% passenger cars
Five or more lanes for one direction
Interchange spacing at 2 mi or greater
Level terrain (grades no greater than 2%)
Drivers primarily regulars
8/9/2019 Highway Capacity Lecture 1&2
11/63
LOS for Freeways
Defined by density (k)
A: k 11 (Smin =480 ft), free flow
B: k 18 (Smin =290 ft), reasonably free flow
C: k 26 (Smin =200 ft), nearly free flow speed;maneuvers limited; reduced comfort
D: k 35 (Smin =150 ft), reduced speeds; limited
freedom to maneuver; potential for queuing
E: k 45 (Smin =120 ft), at capacity; unstable flow F: extensive queuing behind breakdown pts
8/9/2019 Highway Capacity Lecture 1&2
12/63
LOS Criteria
Table 7-1, p.229
Volume-to-capacity
ratio
8/9/2019 Highway Capacity Lecture 1&2
13/63
Speed-flow Curves and LOS forBasic Freeway Segments
Fig 7-3, p.230
K = q/v
Capacity
8/9/2019 Highway Capacity Lecture 1&2
14/63
Freeway Capacity Analysis
Determine flow rate
Determine free flow speed
Determine level of service
8/9/2019 Highway Capacity Lecture 1&2
15/63
Determining Flow Rate
Adjusting hourly volumes or estimates, typicallyreported in veh/h, to arrive at an equivalentpassenger-car flow rate in passenger cars per hour(pc/h)
8/9/2019 Highway Capacity Lecture 1&2
16/63
Determining Flow Rate
Peak Hour Factor (PHF)
Accounting for variation in traffic flowwithin an hour
On freeways, typically ranging from 0.80(rural/off-peak) to 0.95 (urban)
If possible, field data should be used
8/9/2019 Highway Capacity Lecture 1&2
17/63
Determining Flow Rate
Heavy Vehicle Adjustment Factor
Accounting for the presence of heavyvehicles (trucks, buses, RVs)
8/9/2019 Highway Capacity Lecture 1&2
18/63
Passenger-Car Equivalents
Values of ET
and ER
selected for one of
the following conditions:
Extended freeway segments
Specific grades
Downgrades
8/9/2019 Highway Capacity Lecture 1&2
19/63
Passenger-Car Equivalents
Extended freeway segmentsno one grade of 3% or greater is longer than0.25 mi or no one grade of less than 3% is
longer than 0.5 mi
Level: includes short grades of no more than 2%, HV operate at thesame speed as PC
Rolling: HV substantially slower than PC but do not operate at crawlspeeds for significant length of time
Mountainous: HV operate at crawl speeds for significant length of time
8/9/2019 Highway Capacity Lecture 1&2
20/63
Passenger-Car Equivalents
Specific Gradesgrade of more than 0.5 mi for grades less than3% or grade of more than 0.25 mi for grades of
3% or more
Table 7-3, p.232
8/9/2019 Highway Capacity Lecture 1&2
21/63
Passenger-Car Equivalents
Specific Grades
Table 7-4, p.233
8/9/2019 Highway Capacity Lecture 1&2
22/63
Passenger-Car Equivalents
Downgradeswhen trucks must often use low gears to avoidgaining too much speed and running out of
control
Table 7-5, p.233
8/9/2019 Highway Capacity Lecture 1&2
23/63
Determining Flow Rate
Driver Population Factor
Accounting for the presence of unfamiliarusers
Range from 0.85 to 1.00
Use 1.00 unless evidence suggestsotherwise
8/9/2019 Highway Capacity Lecture 1&2
24/63
Freeway Capacity Analysis
Determine flow rate
Determine free flow speed
Determine level of service
8/9/2019 Highway Capacity Lecture 1&2
25/63
Determining FFS
FFS: mean speed of passenger carsmeasured during low to moderate flows
Two methods:
Field measurement Weekday off-peak hours
No adjustment needed
Estimated based on physical characteristics of
the freeway segment
8/9/2019 Highway Capacity Lecture 1&2
26/63
Estimating FFS
8/9/2019 Highway Capacity Lecture 1&2
27/63
Estimating FFS
Adjustment for lane width
8/9/2019 Highway Capacity Lecture 1&2
28/63
Estimating FFS
Adjustment for lateral clearance
8/9/2019 Highway Capacity Lecture 1&2
29/63
Estimating FFS
Adjustment for number of lanes
8/9/2019 Highway Capacity Lecture 1&2
30/63
Estimating FFS
Adjustment for interchange density
8/9/2019 Highway Capacity Lecture 1&2
31/63
Freeway Capacity Analysis
Determine flow rate
Determine free flow speed
Determine level of service
8/9/2019 Highway Capacity Lecture 1&2
32/63
Determining LOS
Based on the equivalent passenger-carflow rate (Vp) and adjusted free-flow speed
(S)
Step 1
8/9/2019 Highway Capacity Lecture 1&2
33/63
Determining LOS
Step 2
8/9/2019 Highway Capacity Lecture 1&2
34/63
8/9/2019 Highway Capacity Lecture 1&2
35/63
Practice Problem
BFFS = 70 mph (LOS A or B)
N = 3, LC = 3ft, Lane Width = 11ft
1 interchange/mi
V = 3080 veh/hr (1-dir)
PHF = 0.88
154 Tr & Buses
Level terrain All commuters
Determine density (D) and LOS
8/9/2019 Highway Capacity Lecture 1&2
36/63
8/9/2019 Highway Capacity Lecture 1&2
37/63
Housekeeping
Exam I grades available; seeGhazan for question sheets
Entire Chapter 7 (K&L) and HCM Ch23
Homework Assignment #4 due at1:20pm next Wed, Oct 24
8/9/2019 Highway Capacity Lecture 1&2
38/63
Highway Capacity (II)
Oct 29, 2009
8/9/2019 Highway Capacity Lecture 1&2
39/63
Learning Objectives
To perform capacity analysis for multilanehighways
To perform capacity analysis for two-lanehighways
To distinguish differences in analysis methodsfor freeway/multilane highway/two-lanehighway
(Chapter 7; HCM Ch23)
8/9/2019 Highway Capacity Lecture 1&2
40/63
Practice Problem
BFFS = 70 mph (LOS A orB)
N = 3, LC = 3ft, LW =11ft
1 interchange/mi V = 3080 veh/hr (1-dir)
PHF = 0.88
154 Tr & Buses
Level terrain
All commuters
Determine density (D)and LOS
8/9/2019 Highway Capacity Lecture 1&2
41/63
Freeway AnalysisApplications
Operational analysis
Given geometric and traffic conditions, estimatespeed, density, and LOS
Design Given forecasted demand volume and desired
LOS, determine number of lanes needed
Planning
Given forecasted AADT (annual average dailytraffic), HV%, and terrain type, estimateoperational and design parameters
8/9/2019 Highway Capacity Lecture 1&2
42/63
Freeway AnalysisApplications
Planning (cont.)
First step: convert AADT to DDHV(directional design hour volume)
K: proportion of AADT occurring in peak hour
0.08-0.09 (urban), 0.15-0.20 (rural)D: proportion of peak hour traffic in the heavier
direction
0.52 (urban circumferential fwy),
0.55 (urban radial fwy), 0.75 (rural fwy)
DKAADTDDHV dayvehhrveh )/()/(
8/9/2019 Highway Capacity Lecture 1&2
43/63
Multilane Highways
4 to 6 lanes
Often with physical medians or two-way left-turn lanes
Posted speed limit of of 40~55mph
Flow not as efficient as freeways
8/9/2019 Highway Capacity Lecture 1&2
44/63
Multilane Highways
8/9/2019 Highway Capacity Lecture 1&2
45/63
Multilane Highway Analysis
Minor differences in base conditions Minimum lane widths of 12 ft
Objects no closer than 6 ft from the edge of the traveled pavement(at the roadside or median)
No direct access points
Divided highway
FFS of 60mph pr more
100% passenger cars
Drivers primarily regulars
Similar to freeways Determine flow rate
Determine free flow speed
Determine level of service defined by density
8/9/2019 Highway Capacity Lecture 1&2
46/63
Determining Flow Rate
Same as freeway analysis
8/9/2019 Highway Capacity Lecture 1&2
47/63
Determining FFS
Two methods:
Direct measurement Low-volume
conditions (below
1400 pc/h/ln) No adjustment
needed
Use a baseline andadjust it
Use BFFS of 60 mphor estimate based onthe 85th percentilespeed
AMLCLW ffffBFFSFFS fLW
=adjustment for lane width(mph)
fLC=adjustment for right-shoulder lateral clearance(mph)
fM=adjustment for median type(mph)
fA=adjustment for accesspoints (mph)
L Width Adj t t
8/9/2019 Highway Capacity Lecture 1&2
48/63
Lane Width Adjustment(fLW )
Base condition (fLW = 0)
Average width of 12 ft. or wider across alllanes
From Highway Capacity Manual, 2000
Same as Freeway LOS
AMLCLW ffffBFFSFFS
Table 7-11
L t l Cl
8/9/2019 Highway Capacity Lecture 1&2
49/63
Lateral ClearanceAdjustment (fLC )
Base condition (fLC = 0)
12 ft or greater TLC
From Highway Capacity Manual, 2000
LRLCLCTLC +=
AMLCLW ffffBFFSFFS
Table 7-12
Multilane Highway LOS
8/9/2019 Highway Capacity Lecture 1&2
50/63
Median Adjustment (fM)
Base condition (fM = 0)
Divided highway
From Highway Capacity Manual, 2000
AMLCLW ffffBFFSFFS
Table 7-13
A P i t D itMultilane Highway LOS
8/9/2019 Highway Capacity Lecture 1&2
51/63
Access-Point DensityAdjustment (fA)
Base condition (fA = 0)
0 access points per mile
For NAPM 40: fA = 0.25 #access point/mi
For NAPM > 40: fA = 10
Default density give by Table 7-15
From Highway Capacity Manual, 2000
AMLCLW ffffBFFSFFS
Table 7-14
8/9/2019 Highway Capacity Lecture 1&2
52/63
Determining LOS
Same procedure as forfreeways
Use vp and FFS curve to
find average passenger
car speed (S) Calculate density
Compare calculateddensity with LOS Criteriafor Basic Freeway
Segments (Table 7-10) orspeed-flow curve (figure 7-5)
Figure 7-5
8/9/2019 Highway Capacity Lecture 1&2
53/63
8/9/2019 Highway Capacity Lecture 1&2
54/63
Two-lane Highways
8/9/2019 Highway Capacity Lecture 1&2
55/63
Two-lane Highways
Undivided two-lane, two-way highways
Class I consistent high-speed operations and
infrequent passing delays Long-distance trips
LOS defined by % time-spent-following andavg. travel speed
Class II Short trips; accessibility
LOS defined by % time-spent-following only
8/9/2019 Highway Capacity Lecture 1&2
56/63
Two-lane Highway Analysis
Base conditions Minimum lane widths of 12 ft
Shoulders at least 6 ft
No No Passing Zones on the highway
No traffic control or turning vehicles Level terrain
100% passenger cars
50/50 split
Either as two-way segments with bothdirections combined or as directionalsegments with each direct consideredseparately
8/9/2019 Highway Capacity Lecture 1&2
57/63
Two-way Segment Analysis
Determine flow rate (iterativeprocedure)
HVG
pffPHP
Vv
=
fHV = Adjustment for heavy vehicle
Same equation, different tables (7-27, 7-28)
fG= Adjustment for grade
Table 7-25 for speed estimation, 7-26
for % time-spent-following estimation
8/9/2019 Highway Capacity Lecture 1&2
58/63
Two-way Segment Analysis
Determine free-flow speed: two methods
Direct measurement
Use a baseline and adjust it
HV
f
FM f
V
SFFS 00776.0
ALS ffBFFSFFS
8/9/2019 Highway Capacity Lecture 1&2
59/63
Two-way Segment Analysis
Determine average travel speed
Determine PTSF
npp fvFFSATS 00776.0
( )pvAnpdeBPTSF fBPTSFPTSF 000879.0 /1100 +fnp = Adjustment for % of no-passing zones
fd/np = Adjustment for directional distribution and
% of no-passing zones
8/9/2019 Highway Capacity Lecture 1&2
60/63
Two-way Segment Analysis
Determine LOS
8/9/2019 Highway Capacity Lecture 1&2
61/63
Two-way Segment Analysis
Determine LOS
8/9/2019 Highway Capacity Lecture 1&2
62/63
Two-way Segment Analysis
Determine LOS
Directional Segment
8/9/2019 Highway Capacity Lecture 1&2
63/63
Directional SegmentAnalysis
Section 5.3 in chapter 7