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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Developing Speed Crash Modification Factors (CMFs) using Strategic Highway Research Program 2 data: Phase 2

Project Information

Project ID:
Project Abstract:

Speed is widely recognized as having serious safety impacts, especially on the severity of crashes. However, these effects are complex and had not been captured in almost none of the Highway Safety Manual (HSM) Part C crash prediction models. These models, known as safety performance functions (SPFs), were developed based on traffic exposure (average annual daily traffic (AADT) and segment lengths) that captures the effect of the other roadway and traffic characteristics through crash modification factors (CMFs). However, there is no CMF developed that reflects the direct effect of speed or speed differentials on safety. The few places in the HSM Part C that reflect a partial effect of speed on safety include:

  • CMF for the effect of automated speed enforcement (several chapters).
  • Speed category (low vs. intermediate or high) vehicle-pedestrian crash prediction models in Chapter 12.
  • Curve speed in the curve CMF on ramps crash prediction models in Chapter 19.

The Strategic Highway Research Program (SHRP) 2 Roadway Information Database (RID) contains roadway and crash data for six states in the U.S. The National Performance Management Research Dataset (NPMRDS) database contains travel time data of 5-minute epochs for the National Highway System (NHS). Both of these databases are developed on a spatial network of links that are matched by over 85 percent. Linking these two databases would provide researchers with a rich source of data with roadway, crash, and operating speed characteristics. The presence of these data categories in a single database provides the researchers a unique opportunity to study the effect of operating speed and/or operating and posted speed differentials on crash frequency and/or crash severity. The most useful of these effects at this point of the development of the Data Driven Safety Analyses (DDSA) are the development of speed-related CMFs for the HSM crash prediction models.

Project Status:
Project Funding Amount (Contract Award Amount):
Start Date:
End Date:
Public Access Plan:
  • Safety Training and Analysis Center (STAC)
Grant/Contract ID:
  • 693JJ320F000092
FHWA Program Area:
  • Safety
FHWA AMRP Program:
  • Safety Data and Analysis
FHWA Activity:
  • Naturalistic Driving Study Pooled Fund

Contact Information

First Name:
Last Name:
Phone Number:
(202) 493-3336
Email Address:
Safety Data and Analysis Team
Office of Safety and Operations Research and Development
Office Code:

Management Organizations

Performing Organization

Organization Role:
Performing Organization
Texas Transportation Institute