Traffic signals are automatic traffic control devices which could alternately direct the traffic to stop and proceed at intersection using red and green traffic light signals as per the pre-determined time settings. The main requirements of traffic signals are to :

(i) Draw attention of the road users
(ii) Enable them to understand the meaning of the light signal (iii) Provide sufficient time to respond and
(iv) Ensure minimum waste of time

Advantages of traffic signals

Properly designed traffic signals at intersections have the following advantages:

(a) Provide orderly movement of traffic at the intersection.
(b) The quality of the traffic flow is improved by forming compact platoons of vehicles, provided all the vehicles move at approximately the same speed.
(c) Reduction in accidents due to crossing conflict, notably the right angled collisions.
(d) Traffic handling capacity is highest among the different types of intersections at-grade.

Disdvantages of traffic signals

(a) The rear-end collision may increase
(b) Improper design and location of signals may lead to violations of the control system
(c) Failure of the signal due to electric power failure or any other defect may cause confusion to the road users.
(d) The variation in vehicle arrivals on the approach roads may cause increase in the waiting time on one of the roads and unused green signal time on other road, when fixed time traffic signal are used