Key highlights on regulations, policies, and program funding for the transportation professional

Effectiveness of Safety Treatments Without Crash Data

Posted: 11/28/2023

NCHRP recently released "Estimating Effectiveness of Safety Treatments in the Absence of Crash Data", which presents a guide for using alternative/surrogate safety measures for developing Crash Modification Factors (CMFs) and other safety performance measures.

CMFs are developed from historic crash data to help safety professionals estimate the expected safety impacts of specific roadway treatments. There has been significant research to develop CMFs for common safety strategies and many are included in the American Association of State & Highway Transportation Officials (AASHTOHighway Safety Manual and FHWA's CMF Clearinghouse.

Supplemental to the report is the web-only document "Estimating Effectiveness of Safety Treatments in the Absence of Crash Data" which describes the process of developing a guide for using alternative, or surrogate, measures of safety for developing CMFs and other quantifiable measures in the absence of crash data.

Read the full report

Who is NCHRP?

The National Cooperative Highway Research Program conducts research in problem areas that affect highway planning, design, construction, operation, and maintenance in the United States.

Administered under the Transportation Research Board (TRB), NCHRP is a collaborative effort between the Federal Highway Administration (FHWA) and the National Academy of Sciences.

Crash Modification Factor

CMFs are a multiplicative factor used to compute the expected number of crashes after implementing a given countermeasure at a specific site.

A CMF reflects the safety effect of a countermeasure, whether it is a decrease in crashes (CMF < 1), increase in crashes (CMF > 1), or no change (CMF = 1).

CMFs are compiled by the CMF Clearinghouse which provides a searchable database easily queried to identify CMFs to meet user needs.

Need More Help?

California LTAP Center

Phone: (562) 985-2872