Police speed enforcement: Effect upon speed and perceived risk of apprehension at different levels of surveillance

The report describes experiments on four stretches of road on which the police increased the level of speed enforcement using stationary methods. The duration of the speed enforcement was 5,4 - 4,8 - 3 and 1,4 hours per day each day for six weeks. Speed was measured before, during and after the period of enforcement increase on each of the experiment stretches of road and on reference stretches of road. Roadside surveys were performed once during and once four weeks after the enforcement period. On the stretches of road applying 5,4 and 3 hours of enfocement per day, the effects were very clear: Both the average speed and the number of speeding drivers were reduced and time halo effects of 10 weeks at the most were observed.