ABSTRACT：Safety performance functions have been a vital tool in traffic safety evaluation including finding contributing factors to crashes, identifying hotspots, and assessing safety effects of countermeasures. In the United States, the Highway Safety Manual has provided a series of SPFs for a variety of road facilities. Due to the limited availability of traffic data in many regions, the transferability of SPFs has been an important topic in the traffic safety field and several studies have been conducted to evaluate the transferability of SPFs. Nevertheless, no study has investigated the international transferability of freeway SPFs and the consistency in hotspot identification has been rarely investigated. Using data from Shanghai and three U.S. states: Florida, Texas and New York, the authors examine the transferability of freeway SPFs between China and the United States. SPFs were developed separately for total crashes, single-vehicle and multi-vehicle crashes. According to the estimated transfer indices (TIs), all Shanghai SPFs are reasonably transferable to U.S. data, but no U.S. SPFs can be transferred to Shanghai data. The modeling results suggest that this discrepancy might be due to the greater sensitivity of U.S. crashes to annual average daily traffic (AADT), and the likelihood that Shanghai crashes are influenced by factors other than segment length and AADT. The method consistency test (MCT) shows that both Shanghai and U.S. SPFs can identify quite consistent hotspots in the other country. The findings from study are expected to be a good reference for researchers and practitioners in developing countries who want to understand the transferability and applicability of SPFs in the international context.
Mingjie Feng, Xuesong Wang*, Jaeyoung Lee, Mohamed Abdel-Aty. Transferability of Safety Performance Functions and Hotspot Identification for Freeways of the United States and China. Transportation Research Board 98th Annual Meeting, Washington D.C., USA, 2019. 1.13-17.