Human Factors Investigations of Distracted Driving

A man looks at his cell phone while driving.In 2018, the most recent year for which statistics are available, there were 2841 people killed and an estimated 400,000 people injured in motor vehicle crashes involving distracted drivers (NHTSA, 2020). Many experts believe that these statistics under-represent the number of crashes that involve distraction because they rely on police reports and self-reporting of drivers.  Regardless, these numbers indicate that distracted driving is a dangerous problem that is likely to increase as potentially distracting in-vehicle technology is added to vehicles and as people bring distracting personal electronic devices into vehicles.

What is Distracted Driving?

Distracted driving can be defined as any activity that diverts attention away from activities critical for safe driving. Driving distractions can be categorized into three main areas: visual, manual, and cognitive.

  • Visual distractions are objects or activities that take the driver’s visual attention away from the road and driving environment. 
  • Manual distractions are objects or activities that take a driver’s hands off the wheel. 
  • Cognitive distraction takes a driver’s mind off the road.

An example of a visual distraction is looking at a phone to read a text message.  An example of a manual distraction is dialing a handheld phone. An example of a cognitive distraction is dictating an email to a voice-activated messaging system. Many distractions require visual, manual, and cognitive resources all at the same time. For example, texting on a handheld phone requires all three resources and is considered a visual, manual, and cognitive distraction.

Effects of Distracted Driving

  • Increased time that eyes are off road
  • Increased reaction time to hazards
  • Greater speed variability and slower mean speed
  • Increased lane deviations and lane departures
  • Closer car following

Human Factors Investigations of Distracted Driving

The role that distraction may have played in a vehicle crash is a complex issue that requires experts with specialized knowledge and expertise in the area of human factors.  A human factors expert uses a combination of accident analysis techniques, knowledge of human behavior and performance, and experience investigating vehicle collisions to determine the relevant factors in a crash.  Human factors investigations of distracted driving collisions include an analysis of whether a reasonably attentive driver would have been able to avoid the collision, whether a driver was distracted, and whether distraction was a cause of the collision.  To make these determinations, human factors experts apply the scientific literature on distracted driving to the analysis of a driver’s performance and behavior at the time of the collision.

To scientifically establish that distraction was a causative factor in a collision, several criteria must be met.

  • First, the driver must have been engaged in a distracting activity at the time of the collision (e.g., within 5-27 seconds of the collision depending on the nature of the distraction).
  • Second, the driver must be exhibiting the known effects of distraction at the time of the collision in a manner that contributed to the collision.  It is important to understand that a driver who is engaged in a distracting activity may not be exhibiting the known effects of distraction (e.g., inattention, degraded perception-reaction time) at the time of the collision.  Therefore, evidence that a driver was engaging in a distracting activity at the time of the collision does not, by itself, determine whether the driver was distracted in a manner that was a cause of the collision. 

Distracted driving is a growing issue with a dire impact on the safety of our roadways. While campaigns to address it have been widespread, it remains a significant cause of traffic fatalities, injuries, and collisions. If you have a case involving a motor vehicle accident and believe that distracted driving may have (or may not have) played a role, a Human Factors Expert can help determine whether a driver was distracted and whether distraction was a cause of the collision.