It is widely acknowledged that traffic safety considers and integrates three components: the roadway environment, the vehicle, and the roadway user. Human factors principles explain how road users gather information, make sense of that information, make decisions, and execute actions when traveling on the roadways. Understanding these principles can help identify safety issues and select the most effective countermeasures that address those issues on the roadways. As we move toward a Safe System approach, which aims to eliminate fatal and serious injuries for all road users by accommodating human mistakes and keeping impacts on the human body at tolerable levels, a basic understanding and application of human factors principles will be viable tools for our safety toolbox. With this in mind, the FHWA Office of Safety has developed a technical report, Practical Safety Solutions for Local and Tribal Roads: A Human Factors Approach, aimed at Tribal and local transportation safety practitioners.

Understanding basic human factors principles can be useful when identifying and addressing local and Tribal road safety issues. This understanding can help select the most effective countermeasures for safety challenges. Using plain language, this report provides information on the effects of road users’ actions on roadway safety, and how, when, and where practitioners can use this information to improve safety on their roadways. This report helps road practitioners understand road user capabilities and limitations. Practitioners can then use that understanding to improve safety. The report is a complement, not a substitute, to technical information found in other guidance, such as the Manual on Uniform Traffic Control Devices and the Highway Safety Manual (HSM).

The report defines six basic human factors principles and provides information about using the principles to improve safety:

Photo shows car driving on two-lane road with a sign indicating an upcoming intersection at Little Coal River Road.
Road users should not be expected to read detailed text on a wayfinding sign while entering a curve. The blue sign should be relocated upstream. © 2017 FormulaNone
  • Information Overload: When road users are overwhelmed with information, they make errors. When there is too much information, road users may not have time to locate the most critical information, make sense of it, make decisions, and respond appropriately.
  • Positive Guidance: Road users need information about the road ahead so they can prepare the correct maneuvers. They need accurate information placed in the correct location in a form they can easily understand.
  • User Expectancy: Road users make assumptions about the road ahead. When their expectations are violated, their planned responses will be incorrect, and they may not have time to evaluate the roadway and change their responses quickly enough.
  • Priority of Information Needs: Information that is necessary for basic vehicle control is more urgent than guidance (for example, choosing the correct lane); guidance is more urgent than wayfinding information. When offering information to road users, it is important to consider which level of information they need.
  • Distraction: When road users’ attention is diverted from their primary task, they miss important information about the roadway and other road users.
  • Visual Perception at Night: Nighttime limits the timing, quality, and location of information road users can acquire and use for safe travel.

These principles can help practitioners identify issues and select potential solutions. The report addresses 11 common safety challenges, such as unsignalized intersections and issues on unpaved roadways. It explains how the human factors principles relate to each safety challenge, how they help practitioners anticipate and mitigate human error, and how practitioners can use the principles to select effective, practical solutions. Each safety challenge offers online and print resources and defines technical terms often used when discussing that topic. This easy-to-use report addresses each topic with:

  • WHY is this important?
  • WHEN and WHERE is this useful?
  • WHAT can we do to improve safety?
  • An illustration or photo.
  • Useful terms for further reading.
  • Cross-references to relevant areas in the report.
  • Useful links for additional resources addressing the same topic.

For more information, contact Rosemarie Anderson at