Preparing Florida for Deployment of SafetyAnalyst for All Roads
The Federal Highway Administration (FHWA) has released a new safety analysis system known as SafetyAnalyst (http://www.safetyanalyst.org /). The system is aimed at providing the state and local highway agencies with a comprehensive set of tools to enhance their programming of site-specific highway safety improvements. The Department plans to take full advantage of the new capabilities of SafetyAnalyst to enhance the safety improvement programs in the stateónot only for the on-system roads, but also the off-system roads that are critical to the overall performance of the state's highway system. In order to do so, the Department must first address four major research and development needs.
First, SafetyAnalyst is designed to account for the regression-to-the-mean (RTM) bias which exists in the current practice of selecting projects for safety improvements. The RTM selection bias is a direct result of the general practice of selecting high-crash locations for safety improvements, which in turn results in the overestimation of crash reduction factors. To address this bias, SafetyAnalyst implements the Empirical Bayes (EB) method which requires the use of safety performance functions (SPFs). SPFs are mathematical relationships that link crash occurrence to traffic and roadway characteristics. SafetyAnalyst is expected to include a set of default SPFs developed from studies throughout the U.S. and Canada. To better represent local crash experience, however, it is preferred that local SPFs reflective of Florida's conditions be calibrated. The University of Florida (UF) Transportation Research Center (TRC) is currently under contract to the FDOT Research Center to conduct a study to re-calibrate those SPFs given in the Highway Safety Manual (HSM) for Florida conditions.
Second, SafetyAnalyst requires average annual daily traffic (AADT) as an input. The Department currently estimates AADT using both short and long-term traffic counts for all on-system roads. However, such estimates are not currently available for off-system roads. This will prevent some local agencies that do not have AADT data (or do not have AADT data with sufficient quality) from using SafetyAnalyst. Accordingly, research is needed to identify and implement methods to estimate AADTs for off-system roads. In addition, for local agencies with AADT data, development effort is needed to acquire and process the data such that they are in a format that can be used in SafetyAnalyst.
Third, the Department is expected to lead the introduction of SafetyAnalyst to local agencies and participate in enabling these agencies to make effective use of the system. Application by local agencies represents an added return to the Department for its effort in creating a one-map base map and in geocoding the crash records for all roads. To allow local agencies to apply SafetyAnalyst, a development effort is needed to map the network and crash databases (for all roads) to the standard input data formats required by SafetyAnalyst. The Department contracted with the University of South Florida (USF) last year to map the crash records from the CAR system for use in SafetyAnalyst. However, crash records from CAR are limited to only those crashes which occurred on the state roads. There is a need to extend this work to the crash records on the off-system roads.
Fourth, SafetyAnalyst is expected to provide functions that will facilitate the use of GIS. The system, however, will not include a GIS component; rather, it will provide only the data interface needed to exchange GIS data between an agency's GIS system and SafetyAnalyst. Given the spatial nature of crash analysis, it is highly desirable that GIS be part of Florida's application of SafetyAnalyst. Research and development efforts are needed to design and develop a GIS system that will work with SafetyAnalyst.
The objectives of this project include:
- Develop SPFs not included in the project of the aforementioned UF study.
- Modify an existing dynamic segmentation program previously developed by FIU to generate the necessary input data suitable for SPF calibration.
- Make the modified dynamic segmentation program available to the UF study and provide technical support as needed.
- Implement a procedure in the Florida Traffic Safety Portal to allow local agencies to upload AADT data.
- Develop a procedure to convert and merge local AADT data to the all-road network being developed by the Safety Office.
- Study the mapping approach being developed by the aforementioned USF study.
- Develop a program to map crash records for all roads (instead of just the state roads from CAR).
- Develop a GIS system to allow the users to graphically select site locations and to display results from SafetyAnalyst.
- Develop a new page in the Florida Traffic Safety Portal to allow users to download ready-to-use SafetyAnalyst data sets, the install program for the GIS system, and any related documents.