Abstract
A before and after study was carried out into the influence on traffic congestions and waiting times of a new introduced ramp metering system at the Coentunnel in Amsterdam. The capacity of the Coentunnel has not changed, which is in accordance with American experiences. The traffic intensities have changed and the route choice has been influenced. The driver behaviour in merging has much improved and road users accept the system very well. The number of accidents has decreased.