Speed cameras

Speed camera enforcement is most appropriate if crashes are clearly concentrated on specific road sections and are related to excess speed, and when the volume of traffic makes physical policing a time-consuming, less effective approach.

The best estimate is that automatic camera enforcement results in a crash reduction of 15 to 20% [19]. Individual evaluation studies differ widely in the reported effects. The actual effectiveness depends on many factors, such as the actual enforcement effort, the initial speed and safety level and the type and amount of supporting publicity.

Without having the pretension to be complete, Table 1 presents the findings of a number of studies of the effectiveness of different speed camera techniques.

Table 1 Overview crash reduction effects studies speed enforcement

It can be seen in Table 1 that favourable results have been obtained both with visible cameras [16][25] and with hidden cameras [29][38].

Whether visible or invisible cameras should be preferred depends upon different considerations. For example, if it is very important that road users lower their speed on a specific section of the road, e.g. because of an intersection or a nearby school, it is more effective to have a visible speed camera, preferably accompanied by a warning sign. On the other hand, hidden cameras, and in particular hidden mobile cameras make speed checks less predictable. Hidden (mobile) speed cameras are often accompanied by a warning sign. This approach may increase the preventative effect, since drivers know that there is a chance of detection but they do not know when and where exactly.

Whereas nearly every driver keeps within the speed limit when a camera is clearly visible, a small percentage of drivers may still violate the limit when they drive on a road with hidden cameras. On the other hand, clearly visible speed cameras drivers may tempt drivers to speed up again a few hundred metres after the camera, while they may be less tempted to violate the speed limit when they are aware of the possibility of a hidden camera check.