Keith Knappkknapp@iastate.edu email >
About the research
The majority of crash fatalities in the United States occur along rural roadways. These roadways typically have low volumes and widespread crashes. In other words, no one location generally has an unexpectedly high number of crashes. Systemic safety tools/methodologies can be used in this type of situation because they evaluate and prioritize expected crash risk through the consideration regional data patterns, research results, and engineering judgment. This project investigated two systemic safety tools/methodologies: the approach followed to produce Minnesota county road safety plans (and now described in the FHWA Systemic Safety Project Selection Tool) and usRAP. Both tools/methodologies were applied with data collected from two counties in Iowa and a sensitivity analyses completed on their results. It was concluded that changing the “weight” of the safety risk factors considered as part of Minnesota approach could have an impact on some of the locations in the “top 20” of the rankings and subsequent decision-making. However, the amount of that impact varied and a correlation analysis of the original and alternative rankings developed found a statistically insignificant difference. The change in acceptable benefit-cost ratio for the application of usRAP showed that it impacted the type and number of countermeasures, along with the benefit-cost ratio of the plan suggested by the software. It is recommended that additional research be completed to consider similar input variable changes on transportation systems with a higher level of variability in their characteristics.