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Crash Modification Factors in Practice: Quantifying Safety in the Roadway Safety Audit Process - Michigan Case Study

Summary from Crash Modification Factors in Practice: Quantifying Safety in the Road Safety Audit Process

(The Michigan case study begins on Page 11 of the full report, after background information about the use of crash modification factors in the Roadway Safety Audit process.)

Publication Year: 2013


Crash Modification Factors (CMFs) can be applied in the Roadway Safety Audit (RSA) process to quantify the safety effects of various treatments and justify the RSA team suggestions to the project owner and/or design team. The following case study illustrates how CMFs have been applied in the RSA process. It also identifies noteworthy practices and actual challenges encountered by agencies with respect to this process.

Project Description

The Michigan Department of Transportation (MDOT) conducted an Operational and Preliminary Design Stage RSA along the first horizontal curve on M-26 north of the village limits of South Range, in Houghton County. The RSA location is circled in Figure 2. This curve was chosen by MDOT on the basis of crash history.

The objectives of the RSA were to:

  • Review road safety at the curve.
  • Identify physical and operational issues that may affect road safety.
  • Review the proposed plan concept.
  • Develop and evaluate potential countermeasures to reduce the frequency and severity of collisions.


The RSA process is typically a qualitative evaluation of the safety performance of a given facility. The RSA report is generally the final deliverable of an RSA team, including a list of potential safety issues and associated countermeasures. It is then the responsibility of the project owner/design team to consider the suggestions identified by the RSA team and determine which countermeasures will be implemented and the relative timeframe for implementation. The application of CMFs not only helps an agency to compare the relative effectiveness of suggested countermeasures, but it also provides information to be used in a benefit-cost analysis. A benefit-cost analysis can be used to prioritize suggested improvements and may be required when applying for funding.

Read the full practice →


Karen Scurry
FHWA Office

Publication Year: 2013

View more information about CMFs on the web at:
Additional practices in the CMFs in Practice Series:

  • Quantifying Safety in the Roadway Safety Management Process - Virginia Case Study
  • Quantifying Safety in the Development and Analysis of Alternatives - Arizona and Colorado Case Study
  • Using CMFs to Quantify the Safety Performance of Design Decisions and Exceptions - California and Missouri
  • Evaluating Opportunities Using Predicted Crash Frequency with CMF Adjustment - Missouri Case Study

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