This report provides a literature review on overseas and domestic variable speed limit (VSL) practices. It includes a comprehensive review of previous literature and also draws upon current thinking and experience of practitioners. The purpose of VSL installations include speed management for safety and for congestion, speed control for inclement weather, incidents, school zones, shopping centres, tunnels, bridges and roadworks. This report summarises reported benefits and costs of VSL installations. Most of the VSL installations were found to have provided significant safety benefits. Although the application of VSL in some cases did not substantially contribute to improved traffic flow, a more homogeneous traffic situation would increase safety and therefore lead to less damage and loss of time for many drivers as well as improved reliability of the traffic system and a positive impact on the environment. Driver behaviour was also changed positively in terms of reduced mean speed, less variance and better compliance. The key operational issues are discussed and summarised. It was found that there are some differences and inconsistencies in place among the operational principles and signage configurations. Practitioners agreed that a driver behaviour study would be helpful in understanding how road users are likely to interpret different sign formats and messages. A study plan including detailed schedule is proposed for the next stage of this project. (Author/publisher)
Samenvatting