ng sts l7 1.ppt

SPECIAL TRANSPORTATION STRUCTURES(Notes for Guidance )Route Location and SurveyRadu ANDREI, PhD, P.E., Professor of Civil EngineeringTechnical University Gh. Asachi IASI

Lecture Seven

Highway design procedures Route Location and SurveyMain ObjectivesGeneral principles for location of land transportation routes. Controlling factors for road and railway locationsRoute survey by ground methods/typical procedureMap study and selection of the best routeLocation surveyProblemsAdditional Readings

Route Location and SurveyMain Objectives The main objectives of this incipient design stage are : to perform specific studies for route location survey to draw preliminary plans and profiles to undertake map study for all reasonable alternative routes and to select the best route

Route Location and SurveyGeneral principles for location of land transportation routes.

The location and construction of various transportation systems, such as railroads, highways, pipelines, airports or waterways are governed by office plans based on field surveys.Along with considerations of economy, feasibility, physical features of the terrain, purpose of the project, right of way and alternate locations available, these land transportation systems are alike in the requirement that the route be as direct as possible between the controlling points, with gradients and curvature held to a reasonable minimum.

Route Location and SurveyGeneral principles for location of land transportation routes.

It is also desirable that the location of the route to be governed by sound engineering principles in order to justify possible future extension or improvement .

Route Location and Survey

Controlling factors for road and railway locationsRoute location, particularly for railroads and highways, is mainly influenced by a number of factors such as the traffic to be accommodated and the physical features of the terrain, generally classified as flat, hilly and mountainous .From the standpoint of drainage conditions of the country, transportation routes may consist of a valley location, a ridge location or a cross-country location.


Controlling factors for road and railway locationsIn flat country the route line might be straight between terminal points, but frequently a change of direction is introduced to reach some of the strategic or compulsory points, to relieve monotony of driving or to avoid certain areas necessitating costly or undesirable property


Controlling factors for road and railway locationsIn hilly and mountainous country a typical railroad route will be a valley location with easy gradients and considerable curvature, following the general direction of the river stream receiving the drainage of the territory


Controlling factors for road and railway locationsA ridge location posses many desirable features such an easy drainage, minimum cuts and fills, and gradients that may be within normal limits.A cross-country location necessitating cuts, fills and bridges is a rule rather an exception for the highways, taking into consideration the fact that long tangents and reduced gradients are necessary for traffic safety and convenience of the operation.


Controlling factors for road and railway locationsOn routes crossing mountainous areas, the gaps or saddles in the ridges are definite points of control from which the route line may proceeded downward of either side of the watershed according to the maximum possible gradient. Such a line has the characteristics of side hill location with uniformly falling grades, curvature conforming to the shape of the ground, thus permitting a good balance of cuts and fills.


Controlling factors for road and railway locationsIn order to reach a summit without exceeding the maximum allowable grade, loops although objectionable are necessary sometimes in the development of the route selection and design.


Controlling factors for road and railway locationsThe engineering procedure establishing the route line and the grade of railroads is essentially the same as that for highways, but relatively greater refinements of gradients and curvature are necessary for a successful railroad operation. Aside for the tractive force required accelerating the train, the locomotive hauling a train of cars must overcome the train resistance, cumulated with grade and /or curve resistance.


Controlling factors for road and railway locationsThe grade resistance is one of the most important factors to be considered in railroad route location. That's why the railroad engineers have defined the so-called "ruling " or "limiting grade, as being the maximum gradient over which a tonnage train can be hauled with one locomotive.


Controlling factors for road and railway locationsWhen a curvature is encountered, the ruling grade is reduced, e.g. compensated for that specific curvature. The recommended compensation value is usually of around 0.04 percent per degree of curve. On main railroads, grades not exceeding 1.00- percent dominant and grades in excess of 2.2 percent are rare. Over fills the grade might be level but in cuts, in order to ensure proper drainage, the grade should not be less than 0.30 percent.


Controlling factors for road and railway locationsThe strip of land on which the roadbed and other railroad facilities are constructed is called railroad right of way, this right of way having a common width varying from 15 to 30 meter and in some cases it may extend to 120 meter.


Controlling factors for road and railway locationsIn order to properly locate and design an important highway, the following information is necessary:- the traffic volume, derived from a traffic census; and origin - destination and delay studies;- the expected traffic load within the lifetime of the highway pavement;- the relation of the highway with the future development of the system;- design standards to satisfy the needs of the expected traffic over a period of years and an adequate right of way.


Controlling factors for road and railway locationsWheneverpossible, moderate curvature and gradients are desirable. For the road users, curvature is preferred to lay straight stretches, the reason being that curvature promotes alertness and relieves the monotony of driving which might cause sleepiness leading to accidents.Excessive highway grades are undesirable :(i)they lead to speed reduction of loaded vehicles, especially for gradients higher than 3%; (ii) they create danger of their descent; (iii) they increase the erosion phenomena at the road surface, shoulders, on ditches.


Controlling factors for road and railway locationsIn regions subject to heavy snowfall the highway should be located with reference to preventing or reducing the drifting of the snow.Also grounds subject to land slides should be avoided if possible.

Route Location and SurveyRoute survey by ground methods/typical procedure

The typical procedure to determine the accepted route for a land transportation infrastructure (railroad, highway, pipeline, or any other transportation system), is as follows:(i)The reconnaissance made by the examination of a wide area, from one terminal point to the other, for the most feasible alternatives;


(ii)The reconnaissance survey and comparison of the route alternatives in sufficient detail, in order to select the best route;(iii)A preliminary survey of the best route, in sufficient detail, for the preparation of planes and estimates of construction quantities;


(iv)The location survey, consisting of laying out, on the ground, the final centreline projected on the maps and competition of plans for the final location;(v)Setting of stakes for construction of the railroad or of the highway including drainage structures, right of way lines, etc.


Map study and selection of the best route

With the reconnaissance and preliminary surveys accomplished and with the contour maps prepared, the next sequence in the process of location of the road or railroad route is the map study for the selection of the best route which will be projected to link the A and B terminal points.



Much of the work in connection with this design is done on paper, using the maps of the area upon which the proposed route is tentatively projected, before being finally established on the ground.



As usually, two terminal control points are given in the design, with the scope of projecting a highway or a railroad which to provide an appropriate transportation infrastructure link between them; The straight line liking these extreme pints is called general guide line;



Very often, when the extreme points are located at considerable distance, the design provides also a series of intermediate points, compulsory for the new design route such as important localities, sources of local construction materials, or strategic objectives, etc.; In such a case, the general guide line gets a polygonal shape, any link between successive compulsory points of the route, being treated relative individually, in order to ensure the continuity of the route;



In flat or moderate hill terrain, this study is done by small adjustments or alterations made to the specific route, in order to improve its geometry and to achieve a good balance between the volumes of cuts and fills;



In steep mountain or hilly terrain, this study is done by using the so called method of axe of zero level; This method consists in comparison, on the map, of the existing terrain slope, gt with the maximum route gradient, ga, permitted by the adopted design speed; in this way, between the controlled points of a route, one may obtain a terrain line corresponding to the axe of the route, having gradients less or at least equal with ga;



Let us consider, two successive contour lines C1 and C2, the interval between these contours being e.Between any points M and N located on these contours, the following slope relation can be written, in this relation, d being the distance between the successive contours:tg = e/d



If we want to study the variation of slope between any two points located on the contour map, it is advisable to select a so call study gradient gs,having a value lower then the maximum allowable gradient ga dictated by the design speed imposed for the specific design, (usually gs = 0.8..0.9 ga), and based on this study gradient, one may derive the so called design distance ds, which represent the minimum distance which has to exist between two points of the route, located on any two successive contours, in order to satisfy the imposed condition of axe of zero level : ds = (e/gs)*100, where gs is expressed in percent (%)



After determining the distance study ds, the map study for the selection of the best route is conducted, by taking in the compasses the distance ds, previously transformed in accordance with the map scale, and departing from one of the controlled points, one may begin to conduct the map study ( see the figure the next slide)



The second condition which has to be satisfied by the polygonal lines thus obtained, in order to be selected for a route is that they do not deviate too much from the general guide line, connecting the so called controlled points.. In case that the arc of radius ds does not intersect the adjacent contour, this means that in this area, the line of the greatest slope of the terrain has a gradient smaller than the study gradient, so that, in order to continue the polygonal line one may select any favourable position for the next point, respecting only the condition imposed for a minimum deviation from the general guide line

Finally, repeating this procedure, one may get to the final controlled point B, and from the multitude of the polygonal line thus obtained, it is advisable to select only those which are satisfying both conditions, neglecting those polygonal line which deviate too much from the general guide line or which presents frequent changes and sharp angles.



The second condition which has to be satisfied by the polygonal lines thus obtained, in order to be selected for a route is that they do not deviate too much from the general guide line, connecting the so called controlled points. In case that the arc of radius ds does not intersect the adjacent contour, this means that in this area, the line of the greatest slope of the terrain has a gradient smaller than the study gradient, so that, in order to continue the polygonal line one may select any favourable position for the next point, respecting only the condition imposed for a minimum deviation from the general guide line



Finally, repeating this procedure, one may get to the final controlled point B, and from the multitude of the polygonal line thus obtained, it is advisable to select only those which are satisfying both conditions, neglecting those polygonal line which deviate too much from the general guide line or which presents frequent changes and sharp angles.



The polygonal lines thus selected should be than compensated, as shown in the next slide, in order to reduce the number of the tangents and of the angles, the compensated route getting an average gradient whites usually is greater than the study gradient gs but less or at least equal with the maximum allowable gradient ga; finally these compensated routes shall by studied in detail, with the consideration of the longitudinal and transverse profiles.


Location survey

The location survey consists in laying out on the ground, the final centreline which has been projected and determined on maps. During the location survey, tangents, curves and drainage structures are established by means of a continuous transit survey, taking into account any necessary adjustments in the line and grade.All the topography with property corners, including the right of way shall be measured from the surveyed centreline, as the staking of the centreline is progressing.


Special Survey

Special surveys will include ground surveys for minor improvements such as the reconstruction or the resurfacing of a highway, long surveys for right-of-way descriptions, or for grade-crossing elimination, site surveys to obtain information needed for the design of large culverts, bridges or interchanges, and for subsoil studies.


Construction SurveyThe construction survey is done as a guide to the Contractor preceding the actual construction of the facility. This survey will include the resetting, when necessary, of the location centre line stakes with sufficient offset stakes, and special surveys for the layout of culverts or bridges, grade elimination structures, turnouts, possible changes appeared during construction, finish grade stakes, etc.;

Problems 1.For a given contour map, drawn at the scale 1:1000, undertake the appropriate route study for a two-way road link, between the terminal points A & B , by using the method of the ax of zero level. Start your route study on the map with a maximum permitted gradient ga = 4%.

Problems 2.Produce at least three alternatives routes and then proceed with the compensation of the polygonal lines thus obtained, by drawing the appropriate intersecting tangents.

Additional ReadingsDorobantu S. si al. Drumuri, Calcul si Proiectare, Editura Tehnica Bucuresti, 1980..Vlad, N., Intretinerea, exploatarea si siguranta circulatiei la calea ferata, Institutul Politehnic Iasi,1992.Lucaci Gh., Costescu I.,Belc F., Constructia drumurilor, Editura Tehnica Bucuresti, 2000

Additional ReadingsAndrei R. Land Transportation Engineering, Technical Publishers, Chisinau, 2002Garber j.N., Hoel A.,L, Traffic and Highway Engineering, revised second edition, PWS Publishing,1999.Zarojanu Gh. H, Popovici D., Drumuri-Trasee, Editura Venus, Iasi, 1999.Hikerson F.T., Route Location and Design, Mc Graw Hill, 5-th edition, 1967.Babkov V., Zamakhaev M., Highway Engineering, Mir Publishers, Moscow, 1967

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