Abstract Manager

The BC Ministry of Transportation and Transit (MoTT) is upgrading Highway 1 with the Fraser Valley Highway 1 Corridor Improvement Program. One project under this program is the design build Highway 11 Interchange.  For the first time, MoTT implemented objective scored elements into the procurement process: looking for innovation and improvements in safety and travel time savings.  Safety is a critical component in the evaluation and scoring of alternative interchange designs. Traditionally, safety has been assessed through benefit–cost analysis based on collision costs (or savings in collision costs), using predicted collision frequency and severity derived from collision prediction models (CPMs). However, most agencies lack locally developed CPMs or sufficiently robust databases to support the development of reliable CPMs for a wide range of interchange configurations. Reliance on models from other jurisdictions, such as the FHWA’s Interchange Comparison Safety Tool (ICST), is also limiting, as it is restricted to a narrow set of standard interchange configurations. Additionally, the ICST relies on a limited set of input variables—such as traffic volumes, number of lanes, intersection angles, and distance to the nearest interchange gore—while omitting other important geometric, operational, and user-related design features that may significantly influence safety, including accommodations for active road users and treatments such as protected versus permissive left-turn movements. Challenged by these limitations, MOTT proposed an alternative, traffic conflict-based evaluation scoring methodology to be implemented during procurement. Moving beyond the traditional practice of simply counting conflict points, the proposed method assessed safety performance by estimating the risk-weighted frequency of conflicts between road users. Conflict frequency was calculated using exposure measures such as traffic volumes and, for active road users, crossing distances, and was then weighted by relative risk factors that reflect the safety influence of geometric design and traffic control features. These risk factors are derived from established research by combining collision modification factors with sound engineering judgment. Overall, the proposed safety scoring approach offers a more flexible and context-sensitive assessment of safety impacts across a broader range of interchange configurations, while reducing reliance on subjective criteria that can be difficult for the owner to evaluate and for bidders to translate into clearly defined, measurable actions and outcomes.  The procurement process including subsequent debriefs with the proponents provided valuable feedback.