Abstract
The Ile-de-France main road operators have carried out several large surveys on on-site experiments to evaluate the present Variable Message Sign (VMS) strategies. This article describes the method used for the surveys to investigate the effects upon both traffic congestion and driver behaviour of the information provided. The attitude of drivers to the information provided was also investigated. A cost benefit analysis was also carried out. The results are presented and include: a) drivers' understanding of the signs, their belief in the information thus provided; b) effects upon traffic flows; c) accident rates; d) traffic deviation; and e) a cost benefit analysis.