Human Factors in Transportation Accidents

Human factors – i.e., human capabilities, limitations, physical conditions, and/or psychological states – play a significant role in transportation accidents. Exponent’s Human Factors scientists and engineers conduct cutting-edge research regarding operator performance in a variety of transportation contexts and environments, how operators interact with vehicular controls and systems, and the types of errors operators make that can contribute to accidents. These research activities, coupled with knowledge of human movement, visual processes, information processing, and cognition, provide Exponent’s scientists and engineers a wealth of expertise that can be applied to the analysis of transportation accidents, vehicle-related product design, and the impact of environmental variables on operator performance. Examples of Human Factors services include investigation of whether operator error (e.g., due to inattention, inexperience, risky behavior, stress) may have caused or contributed to an accident, analysis of accident risk, evaluation of the effects of in-vehicle technology on operators, evaluation of the design features of in-vehicle technology that lead to optimal performance, and analysis of the effect of warnings on operator behavior.


Our Human Factors services have been employed to investigate accidents involving all types of transportation, including:

  • Passenger vehicles
  • Pedestrians
  • Bicyclists
  • Skateboarders
  • Motorcycles
  • Commercial trucks
  • Buses and motorcoaches
  • Trains
  • Industrial equipment (e.g., forklifts, boom trucks, bulldozers)
  • Off-road vehicles (e.g., ATVs, UTVs, snowmobiles)
  • Emergency vehicles
  • Rental vehicles and trucks
  • Aviation 

The majority of vehicular accidents are attributed to human error. Consequently, a critical component of many accident analyses is the examination of the operator. Exponent’s Human Factors scientists and engineers are able to assess the contribution of both intrinsic and extrinsic factors affecting driver behavior. Some examples include:

  • Decision making
  • Demographics (age, gender)
  • Distraction
  • Inattention
  • Drugs and alcohol
  • Driving experience
  • Driver training
  • Familiarity with the vehicle or environment
  • Fatigue
  • Response to the unexpected
  • Risk-taking behaviors
  • Stress, panic, and hypervigilance

In addition, Exponent’s Human Factors team has investigated how design of vehicle-related products, controls, or systems influence safety and/or the effectiveness and performance of vehicle operators. Features studied include:

  • Seatbelts
  • Rearview camera displays
  • Back-up alarms
  • Forward collision warnings with autonomous emergency braking
  • Adaptive cruise control
  • In-vehicle warnings, including lane departure warnings

Our breadth of capabilities and analysis tools ensures that our final product is both rigorous and defensible. We specialize in accident database analysis, surveys and observational data collection, image processing techniques for visibility and conspicuity analyses, and design and execution of experimental research with human subjects. Our vast experience and resources have allowed us to develop expertise in a variety of areas, including but not limited to:

  • Accident avoidance – braking and steering
  • Adaptive cruise control
  • Advanced driver assistance systems
  • Back-up accidents
  • Behavior at curves and intersections
  • Car-following behavior
  • Cell phone usage
  • Effectiveness of alarms and warning information
  • Gaze patterns and visual search
  • Gear shifting
  • Hand controls
  • In-vehicle device usage
  • In-vehicle technology
  • Low-vision situations : nighttime, fog, rain, snow
  • Mirror usage
  • Park-to-reverse incidents
  • Pedal errors
  • Reaction times
  • Seat belt usage
  • Speed and slope estimates
  • Texting while driving
  • Unintended acceleration
  • Sudden acceleration
  • Vehicle egress



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