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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

Commercial Driver Individual Differences Study (CDIDS)


To identify the most critical driver characteristics—such as medical or work histories—that increase crash risk. Note: the final product was eventually renamed the Commercial Driver Safety Risk Factors (CDSRF) study.


In the initial phase of the project, the feasibility of collecting exposure-based risk data for selected characteristics, as well as the feasibility of identifying commercial motor vehicle (CMV) driver factors that contribute to increased risk of large truck crashes, was explored. A follow-on pilot study was performed to determine the relative crash risk associated with driver characteristics, general health and wellness issues, medical conditions, drugs, and other driving performance characteristics. The final phase was a full-scale study, which incorporated lessons learned from the pilot study.


The objective of the case-control Commercial Driver Individual Differences Study (CDIDS) was to examine a wide array of driver and situational factors to determine their prevalence in and relationship to being involved in a crash. The CDIDS sought to identify and prioritize commercial driver individual risk factors that primarily consisted of personal factors such as demographic characteristics, medical conditions, personal attitudes, and behavioral history. These factors also included work environmental conditions, such as carrier operation type and compensation method. Risk factors were identified by linking the characteristics of individual drivers with their driving records through the duration of the study. Of particular importance was the occurrence or absence of critical incidents, including preventable crashes, crashes regardless of preventability, moving violations, and vehicle inspection violations. The study had the following goals:
  • To determine whether individual factors such as demographic characteristics or medical conditions resulted in increased risk for a CMV crash or violation.
  • To determine if there was a relationship between fleet characteristics and protocols and CMV driver performance and health.
  • To identify contributing factors which led to a CMV crash.
  • To track carriers and CMV drivers for up to 3 years after an initial CMV driver survey for identification of additional crash data and validation of study results.


A report that identifies individual factors that increase crash risk.


September 2010: Project began
May 2013: Information collection request approved; data collection began
May 2016: Data collection ended
January 2017: Project completion


FY 2008-10: $3,000,000.00

Current Status:

Project complete—the final report can be read here:

Project Manager:

For more information, contact Terri Hallquist of the Research Division at (202) 366-1064 or


Virginia Tech Transportation Institute