Traffic accidents cause loss of life and property. Proper identification of accident causal factors is essential for composing countermeasures against traffic accidents and reducing related costs. However, two-lane rural roads have distinctive roadway characteristics compared with other types of roads. In order to find cost-effective countermeasures and prioritize roadway safety improvement plans for two-lane rural roadways, a better understanding of the relationship between accident risk and respective characteristics is necessary. This study focuses on accident analysis of two-lane rural roads in Washington State. Six representative state routes (SRs), SR-2, SR-12, SR-20, SR-21, SR-97 and SR-101, are selected as study routes based on their location, length, and geometric characteristics. Along with the six-year (1999~2004) accident data from the Highway Safety Information System (HSIS), roadway video image data and geographical information system data retrieved from Washington State Department of Transportation are employed in this study. Econometric modeling methods are utilized to identify accident causal factors and evaluate their impacts on accident risk at roadway segments and intersections, respectively. Results from the statistical analyses and accident risk models not only help identify accident causal factors, but also provide valuable insights for developing countermeasures against two-lane rural road traffic accidents. (Author/publisher)
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