Traffic signals are control devices that instruct turn-based traffic to stop and proceed automatically using red and green traffic light signals at intersections.

Signs are classified into the following types:

  • traffic control signs
  • fixed time signal
  • manually operated signal
  • Traffic Activated (Automatic) Signals
  • pedestrian sign
  • special traffic signs

1.traffic control signs

traffic signal
traffic signal

These provide three colored light flashes, facing each direction of the traffic flow.

red light indicates pause

Yellow amber light indicates clearance time for vehicles entering the intersection area until the end of the green signal

green light indicates Go

A typical traffic sign showing the arrangement of three light flashes is shown in this fig.

Traffic control signals are further classified into the following 3 types.

a.fixed time signal

These signals are set to repeat the cycle of red, amber yellow and green lights on a regular basis. Depending on the intensity of the traffic, the timing of each phase of the cycle is predetermined. Fixed time signals are the simplest type of automatic traffic signals that are electrically operated.

draw behind signsThe red, yellow and green color wheel goes on regardless of whether there is traffic on any road or not. In heavy current, the traffic has to be stopped at the last stage.

b.traffic active sign

The phase and cycle timings of these signals are changed according to the demand of the traffic.

In semi active signalThe normal green phase of the traffic stream may be extended for a certain period of time to allow vehicles to be diverted from the intersection.

In fully activated signalComputers provide right of way for traffic movement based on the demand of the traffic flow.

C.manually operated signal

In these types of signals, the traffic police monitor the traffic demand from a suitable point during peak hours at the intersection and vary these phases and cycle times accordingly.

2.pedestrian sign

When vehicular traffic is blocked by red or stop signals at road intersection traffic signals, these signals give pedestrians the right to cross the road during the duration of the walk.

3.special signs or flashing beacons

These signs are used to warn the traffic.

When a red flashing signal occurs, drivers of vehicles must stop before entering the nearest cross walk at the intersection or at the stop line where it is marked.

Flashing yellow signals are used to instruct drivers to proceed with caution.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.