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Benchmarking Transportation Safety Performance via Shift-Share Approaches

The measurement of safety performance is a critical task for transportation agencies to monitor the quality of services and evaluate operation efficiency. This article presents and compares safety performance between and among four passenger transportation modes in the United States—highway, transit, railroad, and aviation—using national data from 2002 through 2010. The research utilizes data collected and reported by transportation agencies to meet federal reporting requirements and does not involve the collection of additional data. After a brief review and comparison of transportation-safety performance definitions, the authors evaluate three different types of metrics: number, ratio, and rate, which are applied to all four modes. This article highlights the approach used to compare the share of fatalities/injuries of a particular mode to its share of personal (for highway mode) or passenger (for transit, rail, and aviation) miles traveled compared to the overall multimodal passenger transportation systems. The “shift-share” method is a viable approach to achieve consistent apples-to-apples comparisons. The study shows that aviation and rail are the safest modes for travel between cities, and transit is safer than automobiles for local travel.