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                User’s Guide to Develop Highway Safety Manual (HSM) Safety Performance Function (SPF) Calibration Factors
**Description:**
        This report provides guidelines for calibrating the default safety performance functions (SPFs) in the Highway Safety Manual (HSM). It explains why calibration is needed and provides guidance on how to implement the calibration process (data needs, basis for decisions, and the impacts of the decisions). The guide focuses on the HSM Part C (Predictive Method), applying SPFs with crash modification factors (CMFs) for project-level analysis. The guide is intended for technical experts as well as senior managers, administrators, and decision-makers at state, regional, and local transportation agencies. General calibration procedures versus state-specific procedures are identified and explained.
    
          **Tool Type:**
        Application Guide
    
    
    
          **Owner Source:**
        organization
    
          **Sponsor/Owner:**
        National Cooperative Highway Research Program (NCHRP)
    
        **Published:**
      2014
    
        **Availability:**
      This guide is available free of charge at the following link: User’s Guide to Develop Calibration Factors.
    
          **Disclaimer:**
        This information is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained herein. This information does not constitute a standard, specification, or regulation. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturer's names appear in this information only because they are considered essential to the objective of this publication.
          Any opinions, findings, and conclusions or recommendations, and translations thereof, expressed in this publication are those of the author(s) and do not necessarily reflect the views of the Federal Highway Administration. U.S. DEPARTMENT OF TRANSPORTATION

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