2017 - Research

Safety Study: Reducing Speeding-Related Crashes Involving Passenger Vehicles

The study highlights the scope of speeding-related passenger vehicle crashes, discusses the risks of speeding, dispels common misperceptions about speeding, and makes 19 safety recommendations to reduce speeding-related injuries and fatalities.

Key Takeaway:

  • The National Transportation Safety Board (NTSB) recently discussed a new safety study (final report forthcoming) on passenger vehicle speeding, which examines causes of, trends in, and preventative measures for speeding-related passenger vehicle crashes. The study highlights the scope of speeding-related passenger vehicle crashes, discusses the risks of speeding, dispels common misperceptions about speeding, and makes 19 safety recommendations to reduce speeding-related injuries and fatalities.


  • The exact relationship between speed/speeding and the likelihood of serious and fatal crashes is complex, but speed/speeding increase crash risk by:
  1. Increasing the likelihood of crash involvement.
  2. Increasing the injury severity of a crash.
  • The Manual on Uniform Traffic Control Devices guidance for setting speed limits in speed zones is based on the 85th percentile speed of free-flowing traffic. However, raising speed limits to match the 85th percentile speed can have unintended consequences, such as increasing overall speeds and therefore also increasing the 85th percentile speed. There isn’t enough evidence that this 85th percentile guideline is the best way to establish speed limits. Alternative methods of establishing speed limits exist, which incorporate other factors, such as crash history and the presence of vulnerable road users, like pedestrians.
  • Data-driven speed enforcement programs are necessary for speed limits to be effective. To evaluate the success of such programs, their effectiveness must be measurable and communicable. However, law enforcement reporting of speeding-relating crashes is inconsistent, which means that speeding-related crashes are underreported. As a result, the public tends to underestimate the severity of speeding as a national traffic safety issue, which diminishes effective speeding public education campaigns and data-driven enforcement.
  • Considering the national impact of speeding on crashes, fatalities, and injuries, speeding needs to be elevated as a national traffic safety issue with more federal funding and programming. Unlike other traffic safety issues with a similar impact, such as drunk driving, there currently are no nationwide programs to increase public awareness of the risks of speeding.
  • Automated speed enforcement (ASE) is an effective countermeasure to reduce speeding-related crashes, fatalities, and injuries. However, only 14 states and the District of Columbia use ASE. Federal guidelines for ASE and state laws prohibiting ASE are outdated.
  • Intelligent speed adaptation (ISA) is a vehicle technology that is effective at reducing speeding. ISA uses an onboard global positioning system or road sign-detecting camera to determine the speed limit and adapts accordingly to prevent drivers from exceeding the speed limit. While vehicle manufacturers are increasingly equipping their vehicles with these types of technologies, for the most part they aren’t standard features.


  • While the findings and recommendations from this study are significant, they primarily focus on automobiles. This reflects a need for a more holistic perspective on road users and greater consideration on the impact of speeding vehicles on the safety and experiences of people walking and bicycling.
  • The predominant solution for speeding, the 85th percentile speed limit rule, has negatively impacted traffic safety and fails to account for speeding-related pedestrian injuries and fatalities. We need a more comprehensive and holistic approach that considers the presence of vulnerable road users (i.e., people walking and bicycling) in addition to speed limits to more effectively reduce speeding-related crashes.
  • There is a need for more public awareness campaigns about the dangers of speeding so that stakeholders and the public take it more seriously as a traffic safety issue.
  • There is a need for more data-driven, high-visibility enforcement programs to reduce speeding and disseminate the best practices to local law enforcement agencies. One way to start would be to identify speeding-related metrics (such as the numbers and locations of speeding-related crashes, types of injuries and injury severity levels, speeding citations and warnings, etc.) to establish a consistent framework.
  • Considering the effectiveness of ASE in reducing speeding-related crashes, there should be a review and revision of state legislation prohibiting ASE in states with such laws, as well as a review of federal ASE guidelines.
  • New car safety rating systems are one way to incentivize the standardization of advanced safety systems, such as ISA technology, in new passenger vehicles.


  • The NTSB used mixed quantitative and qualitative methods to summarize the risks of speeding, describe the scope and magnitude of the problem, and explore proven and emerging speeding countermeasures.
  • Quantitative methods include analyses of speeding-related crash data.
  • Qualitative methods include a literature review and interviews with national, state, and local traffic stakeholders: representatives from transportation and highway safety agencies, law enforcement agencies, automobile manufacturers, research institutions, advocacy groups, equipment vendors, personal auto insurance providers, and professional associations.

The National Transportation Safety Board. (2017). Safety Study: Reducing Speeding-Related Crashes Involving Passenger Vehicles.