Abstract
The increasing traffic demand on Dutch motorways calls for more rigorous control than is currently available. In order to develop control systems that can cope with these conditions and can meanwhile maintain an acceptable level of safety we need controlling criteria that provide more detailed information about traffic conditions than the current `classical' parameters. The research reported here led to the development of a first attempt at such a criterion. It is based upon a simple theory concerning traffic behaviour and can easily be calculated from data of standard monitoring equipment. (A)