Presentation
of Traffic Volume Data: - The data collected during the traffic volume studies
are sorted out and are presented in any of the following forms upon the
requirement:
[a] Annual average daily traffic (AADT or ADT): - AADT
the total traffic as well as classified traffic calculated. This helps in
deciding the relative importance of a route and in phasing the road development
programme.
[b] Trend charts showing volume trends over period of years
are prepared. These data are useful for planning future expansion, design and
regulation.
[c] Variation charts showing hourly, daily and seasonal
variations are also prepared. These helps in deciding the facilities and
regulation needed during peak traffic periods.
[d] Traffic flow maps along the routes, are drawn. These
helps to find the traffic volume distribution at a glance.
[e] Volume flow diagram at intersection either drawn to a
certain scale or indicating traffic volume, which showing the details of
crossing and turning traffic.
TRAFFIC CONTROL DEVICES: - The
various aids and devices used to control, regulate and guide traffic may be
called traffic control devices. The most common among these are as:
[1] TRAFFIC SIGNS OR ROAD SIGNS: - Road
signs are used to prevent accidents. Properly designed road or traffic signs
placed at appropriate positions are a must for safe and efficient movements of
traffic. They have been standardized by the IRC and are divided into four
categories:
(a)
Warning Signs: - Warning or cautionary signs indicate to traffic by
suitable standardized symbols the approach of a place where some precaution is
required for the safety of the traffic. The warning signs are provided at a
distance of 100mt on an upgrade 110mt on a level road and 130mt on a down
grade, from the specified danger point.
(b) Prohibitory Signs: - Prohibitory
signs indicate to the traffic that the use of a particular road is prohibited
by a specified class of traffic, or prohibits the sue of horns in a particular
area of the road, or exceed a particular speed limit as on sharp curves, or
parking at a certain place, or from entering into a road.
(c) Mandatory Signs: - Mandatory
signs or regulatory signs indicate to the traffic to comply with certain statutory regulations such as keep left,
turn right etc. the mandatory signs are usually provided at round-abouts, flyovers
etc.
(d) Informatory Signs: - Informatory
signs convey certain information and guidance to the traffic such as road
directions, parking place, direction to a town or city, along with distance
etc.
[2] TRAFFIC SIGNALS: - At intersection where there are a large number of crossing
and right – turn traffic; there is possibility of several accidents as there
cannot be orderly movements. The earlier practice have been to control the
traffic by means of traffic police by showing stop signs alternately at the
cross roads so that one of the traffic streams may be allowed to move while the
cross traffic is stopped. The signals are classified into the following types:
(a) Traffic control signals: - The
traffic control signals have three coloured light glows facing each direction
of traffic flow. The red light is meant for stop, the green light indicates Go
and the yellow light allows the clearance time for the vehicles which enter the
intersection area by the end of green time, to clear off.
(b) Fixed time signal: - Fix time signal or pre timed signals are
set to repeat regularly a cycle of red, yellow and green lights. The timing of
each phase of the cycle is predetermined based on the traffic studies and they
are the simplest type of automatic traffic signals which are electrically
operated.
(c) Traffic actuated signals: - are those in which timings of the phase
and cycle are changed according to traffic demand. In semi0actuated traffic
signals the normal green phase of an approach may be extended up to a certain
period of time for allowing a few more vehicles approaching closely, to clear
off the intersection with the help of detectors installed at the
approaches.