In 1989, the Belgian police started an experiment to try to avoid the congestion that frequently occurred on the main motorway to the coast during summer holidays. A constant reduced speed was forced upon the traffic by policemen on motorcycles that were sent into the traffic stream every few minutes. This method of slowing down the traffic was named `block driving', as the reduction in speed led to the formation of clusters of vehicles (`blocks'). Experiments have shown that block-driving indeed succeeded in avoiding congestion and improving safety. Inspired by this success, plans were developed in The Netherlands to start experimenting with this control measure in 1992. The aim of this paper is to predict whether the block-driving measure could be of any use in a common Dutch problem situation: a bottleneck at a location where an on-ramp merges with the main road. The problem is first analysed qualitatively and then defined in mathematical terms. The conclusion is that block-driving may be successful, but only in specific cases. The results are illustrated by means of an example, which is the intended Dutch pilot site. (A)
Abstract