SPECIAL TRANSPORTATION
STRUCTURES
(Notes for Guidance )
Route Location and Survey
Radu ANDREI, PhD, P.E.,
Professor of Civil Engineering
Technical University “Gh. Asachi” IASI
Lecture
Seven
Highway design procedures
Route Location and Survey
Main Objectives
General principles for location of land transportation routes.
Controlling factors for road and railway locations
Route survey by ground methods/typical procedure
Map study and selection of the best route
Location survey
Problems
Additional Readings
Route Location and Survey
Main 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 Survey
General 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 Survey
General 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 locations
• Route 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.
Route Location and Survey
Controlling factors for road and railway locations
•
In 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
Route Location and Survey
Controlling factors for road and railway locations
•
In 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
Route Location and Survey
Controlling factors for road and railway locations
•
A 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.
Route Location and Survey
Controlling factors for road and railway locations
• On 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.
Route Location and Survey
Controlling factors for road and railway locations
• In 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.
Route Location and Survey
Controlling factors for road and railway locations
• The 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.
Route Location and Survey
Controlling factors for road and railway locations
•
The 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.
Route Location and Survey
Controlling factors for road and railway locations
• When 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.
Route Location and Survey
Controlling factors for road and railway locations
• The 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.
Route Location and Survey
Controlling factors for road and railway locations
• In 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.
Route Location and Survey
Controlling factors for road and railway locations
• Whenever possible, 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.
Route Location and Survey
Controlling factors for road and railway locations
• In 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 Survey
Route 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;
Route Location and Survey
Route survey by ground methods/typical procedure
•
(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;
Route Location and Survey
Route survey by ground methods/typical procedure
•
(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.
Route Location and Survey
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.
Route Location and Survey
Map study and selection of the best route
•
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.
Route Location and Survey
Map study and selection of the best route
•
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;
Route Location and Survey
Map study and selection of the best route
•
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;
Route Location and Survey
Map study and selection of the best 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;
Route Location and Survey
Map study and selection of the best route
•
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;
Route Location and Survey
Map study and selection of the best route
•
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
Route Location and Survey
Map study and selection of the best route
• 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 (%)
Route Location and Survey
Map study and selection of the best route
• 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)
Route Location and Survey
Map study and selection of the best route
Route Location and Survey
Map study and selection of the best route
•
. 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
Route Location and Survey
Map study and selection of the best route
• 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
Route Location and Survey
Map study and selection of the best route
•
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.
Route Location and Survey
Map study and selection of the best route
•
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.
Route Location and Survey
Map study and selection of the best route
Route Location and Survey
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.
Route Location and Survey
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.
Route Location and Survey
Construction Survey
• The 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 Readings
• Dorobantu 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 Readings
• Andrei R. Land Transportation Engineering, Technical
Publishers, Chisinau, 2002
• Garber 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