Systemic safety methodologies risk factor evaluation on low-volume rural paved roadways

Georges Bou-Saab
Keith Knapp

Majority of the fatal crashes in the United States occur on low-volume rural roadways. Therefore, prioritizing roadway elements in rural areas is critical to various transportation agencies due to the wide-spread nature of crashes. Systemic safety methodologies/tools are required in this case since the traditional “hot-spot” method only considers the crash data. Systemic approaches typically use regional data patterns, research findings and engineering judgment to evaluate and prioritize expected crash risk. This research project identified and examined one proactive systemic tool: Minnesota County Roadway Safety Plan (CRSP) which is currently described in the Federal Highway Administration (FHWA) Systemic Safety Project Selection Toolkit. The selected technique was applied on a sample of secondary paved rural roadways in Buchanan and Dallas counties in Iowa. Data was collected along 197 miles in Buchanan County and 156 miles in Dallas County. Initial prioritized ranking lists were generated for the three transportation elements (horizontal curves, stop-controlled intersections and rural segments) that were identified in the Minnesota CRSP approach. The tool was then evaluated to determine if a change in the weight/coefficient of risk factors in each transportation element would have a statistical impact on the prioritized list. Three different sensitivity analysis approaches were designed and tested. Correlation analysis results showed a statistically insignificant difference between the initial and new ranking lists in all cases when the “weight” of the safety risk factors were changed. However, there was an impact on some of the locations in the “top 20” of the rankings and subsequent decision-making. The results of this research should be helpful to state and local transportation safety personnel as they apply the systemic safety tools/methodologies currently available.



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