Police enforcement and road user behaviour.

The effectiveness of police enforcement has been the subject of a series of recent studies in the Netherlands. These studies were concerned with the use of seat belts, speeding (outside urban areas) and drinking and driving. The purpose of the studies has been to compare and improve the effectiveness of different types of enforcement by means of small scale campaigns. The design of the campaigns was based on literature surveys as well as on the results of preliminary studies. It appeared that in all three cases (seat belts, speeding and drinking and driving) enforcement was found to be effective. In these studies the level of enforcement was dependent on the manpower already available for existing enforcement activities. Therefore, the positive effects were obtained with relatively low levels of enforcement. Advance publicity and some evidence of actual enforcement appear to be very essential with these low levels of enforcement. A comparison of the studies on seat belts with those on speeding and on drinking and driving indicates a difference in effects. The improvement of seat belt usage was more easily transferred to other times and places. In the case of speeding the effects have been more limited in time and place, indicating that the information on enforcement has been less convincing or the tendency to test the limits has been stronger. The same is suggested in the study on random breath testing, since the change in drinking and driving was only found at the end of the eight months programme. Finally, attention is paid to the programme of integrated enforcement in the region of Leyden which forms a combination of successful elements of police enforcement of four selected traffic rules: drinking and driving, speeding, the use of seat belts and the proper use of helmets by moped riders.