Traffic safety evaluation is one of the most important processes in the analysis of transportation systems performance. Traditional methods like statistical models and before-after comparisons have many drawbacks such as limited time periods, sample size problems, and reporting errors. The advancement of the traffic conflict techniques combined with the micro-simulation offers a potentially innovative way for conducting safety assessment of traffic systems even before safety improvements are actually implemented. In this paper first simulation-based safety studies are reviewed, and then a modified simulation-based surrogate safety measure and a new simulation-based surrogate safety measure that can capture the probability of collisions as well as the severity of these potential collisions are proposed.Conceptual and computational logic of the proposed surrogate safety indicators are described in detail. These surrogate safety indices are initially proposed for link based analysis and should not be used for other purposes - such as intersection safety assessment - without further enhancements, and the use of these indices should be limited to the analysis of linearconflicts. In addition, these link-based indices are extended to be ableto conduct aggregate network-wide safety assessments. The proposed indices are validated using a well-calibrated traffic simulation model of a section of the New Jersey Turnpike and real accident data from the same section. Preliminary results indicate that there is a strong relationship between the proposed surrogate safety measures and real accident data. Further research is needed to investigate these new surrogate safety indices under different locations and traffic conditions.
Abstract