Transcript LAND TRANSPORTATION ENGINEERING (Notes for Guidance )

SPECIAL TRANSPORTATION
STRUCTURES
(Notes for Guidance )
Highway Design Procedures
Radu ANDREI, PhD, P.E.,
Professor of Civil Engineering
Technical University “Gh. Asachi” IASI
Lecture
Six
Highway design procedures
Determine the volume of current traffic
Determine the project traffic data for future the considered design life of the
road
Select the type and the size of the road in order to accommodate the estimated
traffic demand
Perform studies for route location survey,draw preliminary plans and profiles,
undertake map study for all reasonable alternative routes, select the best
route
Perform detailed study and design for the selected route
Problems
Additional Readings
Determine the volume of current traffic
• Determine the current volume and type
of traffic along the specific desired line (
e.g. where the traffic has to go) of your
project , including the peak loads and
directions.
• You have to acquire sufficient traffic data
in order to account for daily, weekly and
seasonal variations.
Determine the volume of current traffic
• The traffic investigations should be performed by
using manual or automatic , fixed or portable
counters , supplemented by Origine- Destination(
O/D) studies implying Driver Interview ( minimum
sampling 25%) or Driving Postcard ( 100%
distribution desirable).
• Also investigation of speed, travel time and route
by using specific tests conducted in under varied
traffic conditions should be undertaken.
Determine the project traffic data for future the
considered design life of the road
• Fifteen or twenty-year period is usually taken into
consideration for the design life of a road.
• Also you have to review and take into
consideration the regional population trends,
census data, transportation studies available from
the other modes of transport such as railroads, bus
companies and airlines and utility expansion
studies available in the area from telephone, gas
and water-supply companies.
Determine the project traffic data for future the
considered design life of the road
• Regional trends on motor-vehicle registration,
motor-vehicle mileage and public transit use
related with the industry and commerce trends
should be investigated.
• Also the master planning including new or transit
highways, scheduled for activation prior to design
year, should be consulted.
Select the type and the size of the road in order to
accommodate the estimated traffic demand
• At this stage a basic design decision on the degree
of access control must be made and the desirable
design speed shall be established, by using the
average recommended values for judging the
highway capacity, presented in the specific
chapters devoted to highway capacity and design
speed in this course.
• These average data concerning the highway
capacity may be modified and adjusted in
accordance with pertinent local experience.
Perform studies for route location survey,draw
preliminary plans and profiles, undertake map study
for all reasonable alternative routes, select the best
route
• At this stage make the preliminary
plans and profiles based on field
studies for all reasonable alternate
routes which satisfy the desire lines,
analyze and compare them ( see the
next slide )
Perform studies for route location survey,draw
preliminary plans and profiles, undertake map study
for all reasonable alternative routes, select the best
route
Perform studies for route location survey,draw
preliminary plans and profiles, undertake map study
for all reasonable alternative routes, select the best
route
• select the optimal location by comparing cost
estimates, road user benefits, capability of
incorporating the alternates into the regional
master plans, types of vehicles versus feasible
design and operating speeds, traffic safety and
other pertinent factors including the following:
•location of interchanges and
intersections with respect to traffic and
topography;
Perform studies for route location survey,draw
preliminary plans and profiles, undertake map study
for all reasonable alternative routes, select the best
route
• -
frequency of steep grades and the need for slower lanes or
reduced speed for heavy vehicles, thus reducing highway capacity
and traffic safety;
•
right-of-way problems and presence of historical sites ,
cemeteries , etc;
•
suitability to stage construction and appropriate
accommodation of traffic during construction period;
•
effect of local climate , degree of exposition of the road to drifting
snow and ice;
Perform studies for route location survey,draw
preliminary plans and profiles, undertake map study
for all reasonable alternative routes, select the best
route
•location with respect of harmonization
with the other existing transport modes;
• the type and stability of the subgrade soil and
its influence on structural design and costs;
•the impact of the new road on its
environment;
• -
the financial feasibility of project
Perform detailed study and design for the selected
route
• Establish geometric criteria and design speed for
each major segment of the project in conjunction
with preliminary alignment and grade.
• Preliminary intersection design must include in
addition to geometrics, the layout of traffic signs
and pavement markings.
• The aesthetics of landscaping , of views from the
highway and of road structures shall also be
considered in this preliminary stage.
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