Research on Drowsy Driving
Scope of the Problem
Precise counts of crashes caused by drowsy driving are not yet possible. Crash investigators can look for certain clues that drowsiness was likely to have contributed to driver error, but these clues are not always identifiable or conclusive. In lieu of consistent and conclusive evidence, researchers have used various methods to estimate the overall number of crashes or crash fatalities caused by driver drowsiness. These methods range from counts of crash reports where police-reports indicate drowsiness as a contributing factor, to statistical estimates based on crash reports and surveys of self-report crashes or driving experience.
In 2014 there were 846 fatalities (2.6% of all fatalities) recorded in NHTSA’s FARS database that were drowsy-driving-related. These reported fatalities (and drowsy-driving crashes overall) have remained largely consistent across the past decade. Between 2005 and 2009 there was an estimated average of 83,000 crashes each year related to drowsy driving. This annual average includes almost 886 fatal crashes (2.5% of all fatal crashes), an estimated 37,000 injury crashes, and an estimated 45,000 property damage only crashes.
There is ongoing research and discussion about how best to measure the impact of drowsy driving on crashes. A variety of research approaches and data indicate that traditional measures of drowsy driving may significantly underestimate the prevalence of the issue. Researchers have inferred the existence of additional drowsy-driving crashes by looking for correlations with related factors such as the number of passengers in the vehicle, crash time and day of week, driver sex and crash type. One such study from the AAA Foundation for Traffic Safety analyzed data from NHTSA's National Automotive Sampling System (NASS) Crashworthiness Data System (CDS). By using a multiple imputation methodology they estimated 7 percent of all crashes and 16.5 percent of fatal crashes involved drowsy driving. If this estimate is accurate, it suggests that more than 5,000 people died in drowsy-driving-related motor vehicle crashes across the United States last year. The 2009 Massachusetts Special Commission on Drowsy Driving, based on a different research methodology, estimated that there could be as many as 1.2 million crashes, 8,000 lives lost, and 500,000 injuries due to drowsy driving each year.