Abstract Manager

The Safe System Approach aims to eliminate fatal and severe injury collisions by acknowledging that individuals will inevitably make errors. Therefore, transportation systems should be structured and managed to account for human error. Several jurisdictions, including Australia, New Zealand, and the United States, have developed and implemented risk-based procedures to evaluate road safety performance. Austroads introduced the Safe System Assessment Framework, which utilizes a risk-based approach in the form of a safe system matrix. This matrix evaluates various collision types by scoring them in terms of exposure, likelihood, and severity. The product of these parameters across all collision types determines a total score, which can assess the alignment of infrastructure or design alternatives with Safe System principles.

In this study for the Ontario Ministry of Transportation (MTO), the Austroads framework was adopted and further modified to address safety concerns for vulnerable road users in provincial school zones and community safety zones. The modified framework assesses safety issues and mitigation measures, including adjustments to posted speed limits and speed management strategies, aligning with Safe System objectives and identifying necessary improvements. A key innovation in this framework is the addition of decision matrices to streamline and objectively score each collision type. Three decision matrices were developed to evaluate road user exposure (vehicular, pedestrian, and cyclist exposure), collision likelihood, and collision severity. Normalized predicted collisions derived from MTO safety performance functions (SPFs) were used for vehicular exposure. Collision likelihood scoring uses comprehensive decision matrices detailing potential scenarios and circumstances under which specific collisions might occur. For collision severity scoring, thresholds of critical impact speeds for various collision types were used, except for single motor vehicle collisions, which utilized roadside severity indices.

The framework enables the assessment of locations under existing conditions and after implementing countermeasures. A list of countermeasures was developed, categorized by their impact on the framework’s elements. Five case studies were conducted to validate the framework. The results indicate that the framework effectively guides the selection of countermeasures to align locations with Safe System objectives.