The New Jersey Department of Transportation (NJDOT) researched the predictive safety analysis tools available in the market and how they are being used by State Departments of Transportation (DOT). These tools have proliferated since the American Association of State Highway and Transportation Officials (AASHTO) released the Highway Safety Manual (HSM) in 2010. NJDOT sought to understand the benefits, limitations, and paths to implementation for the tools currently in use.NJDOT Research
This research was conducted in two phases. The first phase consisted of a desk scan of predictive safety tool best practices. This phase reviewed nine types of tools. These tools were generally defined by what part of the HSM they address. They include national tools, which cover the most common roadway and safety elements, or statewide tools which are customized to the specific data collected by each DOT. Some agencies devote significant resources to creating their own tools, while other tools are made by external partners that provide specialized knowledge.
The second phase reported on practitioners’ experience implementing HSM predictive safety tools through a survey and six follow-up interviews. This phase found that data needs are more intensive for network screening processes compared with project-level predictive safety analyses. Additionally, the absence of traffic volumes, especially along minor roads, are a common data gap. Finally, this research documents approaches to circumventing technical limitations of HSM predictive safety data.
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