The Surrogate Safety Assessment Model (SSAM) assesses the safety of a design or a flow-control strategy without having to wait for crash data. To assess a traffic facility with SSAM, the facility is first modeled in VISSIM, AIMSUN, Paramics, or TEXAS simulation models and then simulated with desired traffic conditions (typically simulating several replications with different random number seeds). Each simulation results in a corresponding trajectory file. SSAM is used as a post-processor to analyze the batch of trajectory files. SSAM analyzes vehicle-to-vehicle interactions to identify conflict events and catalogs all events found. For each event, SSAM calculates several surrogate safety measures and provides the following:

• A table of all conflicts identified in the batch of analyzed trajectory files, including file, time, location, vehicle identifications, and several measures of conflict severity.
• A summary of conflict counts by type and file, with average values of surrogate measures over all conflicts.
• A filtering mechanism that allows the isolation of subsets of conflicts by ranges of surrogate safety measures, conflict type, network link, or a rectangular region of the network.
• A facility for statistical comparisons of the conflict frequencies and values of surrogate safety measures for two alternative cases or designs using the Student t distribution for hypothesis testing.
• A display of the location of conflicts on the network map, with icons of different shapes and colors assignable to different conflict types or severities.