This resource provides methods and supporting research to help agencies evaluate the safety impacts of Automated Traffic Signal Performance Measures (ATSPMs). While ATSPMs are widely used to improve signal operations, this report enables practitioners to quantify their effects on crash frequency and severity using crash modification factors (CMFs).

Practitioners will gain guidance on applying CMFs to assess safety outcomes associated with signal timing and operational changes, supporting data-driven decision-making for signal optimization and safety performance management. The companion NCHRP web-only document 442 provides the underlying research and methodology used to develop these CMFs, offering additional detail for agencies seeking to replicate or adapt the approach.

Recommended Resource: NCHRP Synthesis 659: Automated Traffic Signal Performance Measures: Management, Operation, and Maintenance examines how state departments of transportation are using high-resolution traffic signal controller data to monitor, manage, and improve signal performance.