TRAFFIC STUDY AND FORECASTING.ppt (Size: 123.5 KB / Downloads: 479)
SEMINAR ON TRAFFIC STUDY AND FORECASTING
MALNAD COLLEGE OF ENGINEERING
Introduction to Traffic engineering
1. TRAFFIC STUDY :
Various Traffic Studies
Presentation of traffic data
2. TRAFFIC FORECASTING:
Data for estimation and period for forecasting
INTRODUCTION TO TRAFFIC ENGINEERING
Traffic engineering is that branch of engineering which deals with the improvement of traffic performance of road networks and terminals.
The study of Traffic engineering may be divided into major section viz..
Traffic studies and analysis.
Traffic operation, control and regulation.
Planning and analysis.
Geometric design &
Traffic Study are carried out
To obtain the knowledge of the type and volume of traffic at present and to estimate future traffic that the road is expected to carry.
To determine the facilities provided on the roads such as traffic regulation and control, intersections, so that improvement on the basis of traffic density may be carried out.
To design the geometric features and pavement thickness on the basis of traffic surveys.
Different traffic studies
1. Traffic Volume study,
2. Speed Studies,
i) Spot speed study
ii) Speed and delay study
3. origin and destination study ( O & D)
1. Traffic Volume Study
Traffic Volume is the number of vehicles crossing a section of road per unit time at any selected period.
The commonly used units are vehicles per day and vehicles per hour.
The various methods available are,
2)Combination of manual and mechanical methods.
4)Moving observer method.
Combination of Manual and Mechanical methods :
It is the multiple pen recorder. A chart moves continuously at the speed of a clock. Different pens record the occurrence of different events on the chart. A particular switch may be pressed whenever a particular class of vehicles arrives and this operates the pen on the channel which can be identified with the arrival of a particular class of vehicle.
Manual counts :
This method employs a field team to record traffic volume on the prescribed record sheets.
In this method first the fluctuations of traffic volume during the hours of the day and the daily variations are observed .
Presentation of traffic volume data
(i) Annual average daily traffic( AADT) or ADT
The total traffic as well as classified traffic are calculated .
(ii) Trend charts
Showing volume trends over a period of years are prepared.
(iii) Variation charts
Showing hourly, daily and seasonal variations are also prepared .
Spot speed is the instantaneous speed of a vehicle at a specified section or location.
Spot speed by Enoscope
It is one of the simplest method of finding spot speed.
Its principle is the observer is stationed on one side of the road and start a stop watch when a vehicle crosses that section ( i.e ,observer) .The enoscope is placed at a convenient distance say 30m to 50m,the moment when the vehicle crosses the section where enoscope is fixed,the stop watch is stopped. Time required to cross the known length is found and is converted to speed in KMPH.
Presentation of spot speed data
Average speed of vehicles
Cumulative speed of vehicles
Cumulative speed of vehicles
3. Origin and Destination Studies
The O & D studies of vehicular traffic determines their number, their origin and destination in each zone under study.
The various applications of O & D studies may be summed up as follows:
To locate expressway or major routes along the desire
To judge the adequacy of parking facilities and to plan for future.
To locate intermediate stops of public transport.
To establish preferential routes for various categories of vehicle including by pass.
Methods for collecting the O & D data
Road-side interview method,
License plate method.
Return post card method,
Tag-on-car method and
The choice of the method is made judiciously depending on the objective and location.
Road-side interview method
The vehicles are stopped at previously decided interview stations, by a group of persons and the answers to prescribed questionnaire are collected on the spot.
The information collected include the place and time of origin and destination, route, locations of stoppages, the purpose of the trip, type of vehicle and number of passengers in each vehicle noted .
Presentation of O and D Data
The data are presented in the following forms:
(i) Origin and destination tables are prepared showing number of trips between different zones.
(ii) Desire lines are plotted which is a graphical representation prepared in almost all O & D surveys
To plan the construction of a new facility of the improvement of existing facilities.
Accurate estimate of future traffic will influence the engineering design of the facility and the economic decision whether to take up the project or not.
Data for estimation:
data on traffic flows,
capacities of different links in the network,
locational pattern of future projects etc.
Methods of forecasting
The mechanical methods simply project forward the past trends, " assuming that future experience is a direct function of past experience."
In an analytical method , historical trend pattern is classified and analyzed.
In urban traffic projections, the most common method is that the projecting the existing traffic pattern determined from origin-destination traffic surveys.
This method is also referred as Gravity model.
The most promising form of the Gravity model is:
For an economic development of our country proper Transportation planning is a must. In the present stage, there is a lack of statistical or traffic data. So, A traffic study such as Traffic volume study, speed study, O & D study. should be conducted throughout the country on a sampling basis to find out the capacities under different topographic conditions, traffic composition, surface conditions for both rural and urban areas and the existing traffic data should be utilised in an optimum way by proper co-ordination between various modes of transport.
Estimation of future traffic by mechanical method and analytical method is done on scientific basis. for estimating future traffic by analytical method, O & D Traffic study gives the better idea for urban areas