Most crashes happen at intersections. Traffic signals are a way to stop conflicting flows of traffic entering the intersection at the same time and can reduce crash risk.

At signalised intersections, priority is assigned to conflicting traffic streams by time separation. They are adaptable to very high traffic volume and are relatively compact. The design of signal schemes needs to satisfy demands for capacity and safety. An adequate time gap is needed between green signals of conflicting movements.

Signals can be set to change according to fixed times, or they can be activated according to traffic demands. It is also possible to link a network of signalised intersections together to provide control of the road network as a whole.

Some signals are controlled manually but often this results in cycle times being too long for maximum intersection capacity. This can cause long delays and driver frustration, which can lead to unsafe driving.

High speed signalised intersections are those where traffic speeds on any one arm is 60km/h or above. These intersections require extra caution in design as they are associated with a dilemma zone making it difficult for drivers to stop or continue when they see an amber light. Additionally, the consequence of right angle collisions or collisions with non-motorised users is often high due to higher traffic speeds.

Traffic signals should be positioned such that they are highly visible to users. The placement of traffic signals should be checked to minimise any risk of users reading the wrong signal or misunderstanding signal displays.