About the research
The main goal of this research project was to evaluate the current Iowa Department of Transportation (Iowa DOT) safety improvement candidate list (SICL) process. A survey of 17 other state departments of transportation was conducted to determine the state of the practice in other areas. The majority of the states use a combination of several different methods, as Iowa does. The most significant difference between Iowa and the other states surveyed is that Iowa uses a much longer analysis period. The first objective of this research was to evaluate whether fatalities overwhelm the current Iowa DOT SICL process. The main conclusion of the analysis was that the SICL process is significantly influenced by fatalities, based on the dollar value given them in the value loss ranking. The second objective was to perform a sensitivity analysis to evaluate impact of the individual ranking methods (crash frequency, crash rate, and value loss) on the final ranking, which results in the final SICL. Results indicate that the contributions of value loss and crash rate to the final Iowa DOT SICL ranking are similar. When the contribution of crash frequency is maximized, significantly less pronounced changes occur, suggesting that the SICL ranking process is more influenced by crash frequency than the other two methods.