Variable Speed Limit Sign (VSLS) systems enable transportation managers to dynamically change the posted speed limit in response to prevailing traffic and/or weather conditions. Although VSLS have been implemented in a limited number of jurisdictions throughout the world there is currently very limited documentation describing the quantitative safety and operational impacts. Furthermore, the impacts reported are primarily from systems in Europe, and may not be directly transferable to other jurisdictions, such as North America. This paper presents the results of an evaluation of a candidate VSLS system for an urban freeway in Toronto, Canada. The evaluation was conducted using a microscopic simulation model combined with a categorical crash potential model for estimating safety impacts. INTR ARIABLE Speed Limit Sign (VSLS) systems consist of dynamic message signs (DMS) deployed along a roadway and connected via a communication system to a traffic management centre. The VSLS are used to display a regulatory or advisory speed limit. Unlike typical static speed signs, the VSLS system enables transportation system managers to dynamically post a speed limit that is appropriate for current traffic, weather, or other conditions. VSLS are thought to improve safety and reduce driver stress while improving traffic flow and travel times [1]. Worldwide, VSLS systems have been deployed in a limited number of jurisdictions including the UK, the Netherlands, the USA, Germany, Australia, and New Zealand. Benefits have been reported from empirical studies in terms of safety with reduced collisions [2, 3] and in terms of improved traffic flow perceived by the driver [4]. Although in general, benefits have been recognized, most of the empirical studies to date are limited by one or more of the following: ODUCTION • Lack of control of important influencing factors such as traffic volumes, degree of enforcement and compliance, etc. • Empirical benefits reported largely in terms of qualitative evidence. • Transferability of results to other jurisdictions (ie. Europe to North America).

Variable Speed Limit Sign (VSLS) systems enable transportation managers to dynamically change the posted speed limit in response to prevailing traffic and/or weather conditions. Although VSLS have been implemented in a limited number of jurisdictions throughout the world there is currently very limited documentation describing the quantitative safety and operational impacts. Furthermore, the impacts reported are primarily from systems in Europe, and may not be directly transferable to other jurisdictions, such as North America. This paper presents the results of an evaluation of a candidate VSLS system for an urban freeway in Toronto, Canada. The evaluation was conducted using a microscopic simulation model combined with a categorical crash potential model for estimating safety impacts.