Control by variable speed signs: results of the Dutch experiment

This paper presents the results of the Dutch experiment with the application of variable speed control on motorways. The measure consists of implementing a reduced speed limit on a motorway section, in order to smooth or homogenise the flow of traffic. The speed limits are implemented only when volume approaches the capacity and are kept constant on a complete (predefined) section of motorway. Only the limits of 90 and 70 km/h are used, and the choice between these two is made each minute, based on measurements of the average traffic speed on the section, such as to keep the difference between average and limit speed small. The aim of the control is not to reduce the average speed, but to reduce speed differences, between and within lanes.