Abstract
This paper considers the effectiveness of intelligent cruise control systems, in particular two types, one purely advisory and the other with an additional automatic distance control function. The advisory system relies on the driver correcting his speed to match the car in front. Braking is applied automatically by the intervention system when the driver does not react. Trials carried out in Berlin as part of the Prometheus project are outlined. Parameters studied were a) journey speeds, b) headway distributions and c) the occurrence of critical situations. The results suggest that safety was significantly improved whilst no capacity reduction was observed.