Variable speed control: state-of-the-art and synthesis.

In its policy to fight traffic congestion, the Dutch Ministry of Transport launched various measures, for example in dynamic traffic management. To achieve the required short-term implementation of variable control of speed limits on motorways, it set up a plan with three stages: investigation of available knowledge, pilot application, and implementation. This paper presents the results of the investigation of the state of the art of variable speed control on motorways. This investigation consisted of a literature study, a working visit to the M25 motorway around London, and a workshop with experts. The most recent relevant literature was studied, from the Fourth Framework Programme of the European Union and from direct contacts. Information about the actually operating state of the art on variable speed control on motorways was obtained from the visit to the M25. The strong similarity between the results of the UK and Dutch experiments was noted, together with the very positive attitudes of drivers towards this type of control. The workshop with Dutch traffic experts and `responsible people' was accompanied by questionnaires, and important agreements and disagreements were noted. The paper finally attempts a synthesis of the investigation's results in an integrated view of the control measures.