Traffic signal warrants (TSWs) are important tools for traffic engineers because they provide an objective shorthand means of identifying whether a net benefit would result from signalizing an intersection. This decision can impact numerous operational facets; consequently, most TSW systems consider several factors when estimating an overall impact.
The Canadian Traffic Signal Warrant Matrix Procedure, originally published by the Transportation Association of Canada (TAC) in 2003 with subsequent minor adjustments, does not have a collision history component: a common feature in other TSWs. This creates challenges for practitioners investigating the safety impacts of signalization because the lack of a standardized approach can lead to inconsistency in their findings.
This research developed collision adjustment factors (CAFs) that convert the collision history for a site into points that supplement the existing TAC warrant procedure score outputs. The CAFs were developed based on recent research that estimates expected changes in collision severity and frequency in North America due to signalization, with the intent that they can be broadly used by all Canadian jurisdictions. Additionally, the procedure used to develop the national CAFs in this research can be employed by jurisdictions analyze their intersections based on local data.