Uncertainty exists in the evaluation of the contribution of Variable Message Signs (VMS) especially dynamic speed limits for traffic safety in the course of a Motorway Control System (MCS). The use of Permanent Traffic Signs (PTS) in combination with ramp metering to achieve the same positive effects is under increasing discussion. The study describes the effects of PTS and VMS to sign the traffic regulations on motorways. The investigation bases mainly on the evaluation of traffic safety of a long distance motorway in Rhineland-Palatinate. For the long distance motorway the posting of speed limits and other traffic regulations by PTS and VMS was carried out in two steps. In the first step a permanent speed limit of 130 kph and forbidding of over-taking for heavy vehicles were posted. For an accident-prone motorway section of 23 km a MCS was installed three years later to increase traffic safety and to optimise traffic flow conditions. The posting of a permanent speed limit and forbidding of over-taking for heavy vehicles at the long distance motorway cause a reduction of accident and accident costs of about 30 %. The evaluations in more detail show the necessity to differ between accidents influenceable and non-influenceable by a MCS. The implementation of the MCS produced a further light improvement of traffic safety by an overall analysis, but in the case of accidents influenceable to MCS a clear improvement. The evaluation of the metropolitan motorways presents a concentration of the accident occurrence at the access points and interchanges. PTS - here speed limit and forbidding of overtaking of heavy vehicles in combination with ramp metering - seems to be an equivalent alternative to a "classic" MCS for motorways in metropolitan areas. Analysing cost-benefit of MCS a reduction of the accident costs has to take into account carefully in the case of existing speed limits and other traffic regulations by PTS. For the covering abstract see ITRD E135448.
Samenvatting