Updates of Florida Crash Reduction Factors and Countermeasures to Improve the Development of District Safety Improvement Projects
Crash reduction factors (CRFs) are used to estimate the expected reduction in crashes that will occur during a given period as a result of implementing a proposed countermeasure. This estimate is important in carrying out an economic evaluation of potential countermeasures.
In 1987, the Department contracted with the University of Florida (UF) to develop a set of CRFs based on 237 improvement projects submitted by Florida Department of Transportation (FDOT) District Offices. In the study, a total of 103 countermeasures were identified and selected for analysis, but data were available for only 58 of the countermeasures. Of the 58 countermeasures that have data, only 24 were found to have resulted in significant reduction in total crashes.
To better serve the needs of its District Offices, the following problems associated with the existing CRFs need to be addressed:
- At the time of the UF study, forty four percent of the 103 countermeasures selected for analysis did not have any improvement projects that could be used to develop CRFs. As a result, CRFs for many countermeasures are not available and “imported” CRFs from states such as New York and Arizona have been used.
- In the UF study, the average number of improvement projects used to develop the CRF of each countermeasure was a low four. In addition, thirty-six of the 58 countermeasures were developed based on crash experience of two or less improvement projects. The small sample size may have contributed to the fact that existing CRFs often predict crash reductions that were vastly different from the actual field experience.
- The UF study examined a total of 103 countermeasures. Since then many additional countermeasures, with the aid of rapidly developed advanced technologies over the past decade, have been identified and implemented. The CRFs for these new countermeasures need to be developed. In addition, descriptions for the 103 countermeasures have been overly general and do not help the traffic engineers to identify the more detailed designs associated with a specific improvement. These countermeasures need to be refined with additional details.
Since the completion of the UF study in 1988, hundreds of safety improvement projects have been implemented throughout the state. This project will take advantage of the availability of these additional data to update and improve CRFs for Florida. The specific objectives are:
- Perform a thorough review of the literature to learn about the state-of-the-art research in CRFs and countermeasures.
- Conduct a survey of all U.S. State Departments of Transportation (State DOTs) to identify the state-of-the-practice in CRFs and countermeasures.
- Update existing Florida CRFs with data from additional safety improvements projects to improve their accuracy.
- Develop CRFs for countermeasures that were not developed in the UF study due to insufficient data to provide a more complete set of CRFs for use by District Offices.
- Develop CRFs for new, viable countermeasures reported in the literature or other State DOTs to make available more countermeasures for District Offices.
Create a database of safety improvement projects and a user-friendly application software to interface with the database to facilitate continued update of CRFs (as more safety improvement project data becomes available) and to apply the CRFs to compute the costs per crash reduced. The application software and database will be applicable to all before-and-after analyses, including those that are not measured by crash reductions.