What is the purpose of a Safety Performance Function (SPF)?

The purpose of a Safety Performance Function (SPF) is to predict crash frequency for specific base conditions. This statistical model utilizes historical crash data and various influencing factors to establish a relationship between roadway features, traffic conditions, and the expected number of crashes. By doing so, SPFs serve as crucial tools in roadway safety analysis, helping engineers and planners understand how different environments or conditions correlate with crash risks.

SPFs are typically used to inform highway safety improvement projects, aiding in the prioritization of interventions based on predicted outcomes. The ability to forecast crash frequency allows for better resource allocation and more effective design decisions, ultimately contributing to improved roadway safety.

The other options do not align with the primary function of SPF. For example, while comparing crash modification factors can be an important part of safety analysis, it is not the primary aim of SPFs. Similarly, providing accessibility for safety data or analyzing the effectiveness of roadway treatments involves different methodologies and focuses than the predictive nature of SPFs.