Abstract Manager

Speed Management is a critical component of a Safe System. However, it is inherently challenging to reduce speed limits in a rural highway context. When severe incidents occur at the intersection of highways with major cross streets, questions arise as to whether changing the speed limit along the highway through the intersection would reduce collision risk. Similarly, achieving speed reduction is a challenge where rural highways approach built-up areas. Manitoba Transportation and Infrastructure (MTI) commissioned a study to review and synthesize research and current practices regarding speed limits and speed management in these two contexts.

The study reviewed speed limit setting methodologies in Manitoba, neighbouring provinces and comparable US States. It also included a review of industry guidance from TAC, FHWA and others, and a literature review of the impact of changing speed limits on safety performance. The review found limited related research on rural highways, and even less for these two particular contexts. While in some cases minor speed limit reductions on rural highways have led to minor collision reductions, major speed limit reductions have led to increases. The limited research available on transition zones suggest that speed limit changes alone have a negligible impact on safety performance. In both the contexts, implementing physical speed reduction measures could have a much greater impact.

The Safe System Approach implies that major at-grade intersections that include left-turn and crossing movements are not recommended within high-speed highway environments due to the likely high impact speeds and low survivability rate. Instead of speed limit reductions, the Safe System Approach promotes alternative intersection designs that relocate these turning movements. In transition zones, the risks are more closely related to driveway density and the presence of vulnerable road users; and human factors needs should dictate the type and location of treatments both in the rural zone and the transition zone, in order to achieve the intended speed reduction.

Recently, MTI has implemented speed reduction treatments within transition zones and rural communities, with positive compliance results. The Department is currently discussing the results of this research and identifying opportunities to pilot more innovative intersection designs based on Safe System principles. With growing confidence for speed reduction compliance, MTI is also reviewing opportunities to pilot further rural speed management measures that will balance safety benefits against high-speed mobility.