scope:

The Highway Safety Manual (HSM) was developed to help measurably reduce the frequency and severity of crashes on American roadways by providing tools for considering safety in the project development process. The HSM assists practitioners in selecting countermeasures and prioritizing projects, comparing alternatives, and quantifying and predicting the safety performance of roadway elements considered in planning, design, construction, maintenance, and operation. The three-volume HSM features a synthesis of validated highway research, procedures for including safety in project decisions, and analytical tools for predicting impact on road safety.

The Highway Safety Manual Supplement includes Chapter 18, Chapter 19, and Appendix B to Part C.