- Average speed control
- Concluding remarks
- Physical policing
- Speed enforcement techniques and their effectiveness
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% . 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.
|Road type||Method type||Effect on crashes||Study and country|
|Urban||Fixed speed cameras||Minus 28%, all crashes||Elvik & Vaa (2004) Meta-analysis worldwide|
|Rural||Fixed speed cameras||Minus 18%, all crashes|
(* corrected estimate, not mentioned in original report)
|Elvik & Vaa (2004) Meta-analysis worldwide|
|Urban||Fixed speed cameras||Minus 22%, personal injury collisions||Gains et al. (2005) UK|
|Urban||Mobile speed cameras||Minus 22%, personal injury collisions||Gains et al. (2005) UK|
|Rural||Fixed speed cameras||Minus 33%, personal injury collisions||Gains et al. (2005) UK|
|Rural||Mobile speed cameras||Minus15%, personal injury collisions||Gains et al. (2005) UK|
|Rural||Fixed speed cameras||Minus 20%, injury crashes||Elvik (1997) Norway|
|Rural||Mobile hidden speed cameras||Minus 21%, injury crashes involving a motor vehicle||Goldenbeld & Van Schagen (2006) Netherlands|
|Highways||Mobile speed cameras||Minus 25%, daytime unsafe speed related crashes||Chen (2000) Canada|
|Highways||Hidden speed cameras (*extra effect above visible cameras)||Minus 11%, all crashes||Keall et al. (2001) New Zealand|
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  and with hidden cameras .
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.