Generally, reviews report substantial positive effects of speed enforcement on both speeding behaviour and the number of crashes  . However, the effects of speed enforcement are by no means as clear cut as one would like. The sizes of the reported effects of speed enforcement, for instance, vary considerably. For example, Pilkington & Kinra  found that evaluation studies reported that the crash and casualty reduction in immediate vicinity of the speed camera locations varied between 5 and 69% for crashes, between 12 and 65% for injuries and between 17 and 71% for fatalities. These differences probably are influenced by the type, intensity and location of the enforcement activities as well as by the situation before the enforcement started.
A recent TRL study  reviewed the literature on police enforcement. With respect to speed enforcement the review concludes that:
- Speed cameras are more effective than physical policing methods in reducing speeds and crashes
- Speed cameras are more effective in reducing crashes inside urban areas than on rural roads
- Fixed speed cameras are more effective in reducing speeds and crashes than mobile speed cameras
Speed camera enforcement should be used for a large concentration of traffic crashes at high-volume traffic locations. Physical policing can be a good alternative to safety camera enforcement when crashes are scattered, and provided operations are randomised and applied to a large part of the network.