traffic studies for planning bypasses around towns

TRAFFIC STUDIESFOR

PLANNING BYPASSESAROUND TOWNS

BYKIRAN CHAPPA2013BPLN028

INTRODUCTION

• A bypass is a road or highway that avoids or "bypasses" a built-up

area, town, or village, to let through traffic flow without

interference from local traffic, to reduce congestion in the built-

up area, and to improve road safety.

• Particulars such as volume,origin,destination and

delays,Pertaining to through and local traffic are required for

justifying the Provision of a bypass.

• Depending Upon its Origin and destination, the traffic going through a town can be classified as:

I. External to External :Traffic whose Origin and destination both lie

outside the town. It is totally Bypassable whereas others traffic is not.

I. External to Internal :Origin of traffic outside and destination inside the town.

II. Internal to External : Origin of traffic inside and destination outside the town.

III. Internal :Traffic whose origin and destination both lie within the town

ORIGIN AND DESTINATION SURVEY

• Selection of survey Points

Survey stations should be located where the approach roads intersect the cordon line drawn to enclose the town under study.

I. The cordon line should be well away from the town for effectively identifying the bypassable traffic.

II. The cordon line should encompass all existing bypasses catering to regional traffic moving around the town.

• The surveys should normally be conducted for seven consecutive days but in any case for not less than three days and must encompass the weekly market and one working day.

METHODOLOGY

Depending upon the size of the town,

the survey can be carried out by any of

the following methods:

1. Registration plate method

2. Tag and disc method

3. Roadside interview method

Registration Plate method :

• Registration number of vehicles and time of entry and exit of the inbound and outbound vehicles are noted down at each survey point.

• This method does not cause any inconvenience to traffic.

• It is suitable for very small towns

Tag and disc method :• The vehicles entering the town stopped at survey points and tags with

entries such as the time of entry, place of entry and type of vehicles are tied to the front of the vehicles. Sometimes Discs are distributed to the drivers.

• When the vehicles leave the town at the cordons, these tags of discs are collected by the surveyors.

Road side interview method :

• Inbound vehicles are stopped at the survey points and information on time of interview, type of vehicle, registration number etc., are noted down by the observer.

• Then the observer puts questions to the driver to get information on origin, destination, purpose of trip and purpose of halts within the town etc.

TRAVEL TIME AND DELAY STUDIES• This study can be conducted by the moving car technique. By this

technique, a test vehicle is run at the perceptible average speed of the traffic stream.

• The survey can be conducted by any one of the following methods:

1. Floating car method : In this method, the driver has to overtake an equal number of vehicles which over take the test car.

2. Average car method :In this method, the driver runs the test vehicle at the average speed which he considers as the average speed of the traffic stream.

3. Restricted car method : this method is the same as average car method. But it overcomes the disadvantage existing in the latter by restricting the speed of the test vehicle under speed flow conditions to predetermined speed limits.

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