UW News

June 9, 2006

Decreased Alcohol Consumption, Increased Use of Seat Belts Save Lives

Traffic crash mortality rates in the U.S. declined by 44 percent between 1969 and 2003, dropping from 26.4 per 100,000 person-years in 1969 to 14.7 in 2003. Behaviors that contribute to the risk of traffic-crash mortality include alcohol use by drivers and pedestrians, not wearing a seat belt, lack of an air bag, not wearing a motorcycle helmet, and not wearing a bicycle helmet.

Of these five risk factors, decreased alcohol consumption and increased use of seat belts were associated with substantial reductions in crash mortality from 1982 through 2001, according to new research by investigators at the Harborview Injury Prevention & Research Center.  The increased presence of air bags and use of motorcycle helmets and bicycle helmets were associated with smaller reductions, the researchers found.

“Changes in Traffic Crash Mortality Rates Attributed to Use of Alcohol, or Lack of a Seat Belt, Air Bag, Motorcycle Helmet, or Bicycle Helmet, United States, 1982–2001” is published in the June 2006 issue of Injury Prevention. The researchers studied data from the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System, which collects information on all crashes on public roads in the U.S. that result in a fatality within 30 days.

There were 858,741 traffic deaths during the 20-year period. The researchers estimated deaths attributed to each factor were:

  • alcohol use, 366,606;
  • not wearing a seat belt, 259,239;
  • lack of an air bag, 31,377;
  • no motorcycle helmet, 12,095;
  • no bicycle helmet, 10,552.

Over the 20 years, mortality rates attributed to each risk factor declined: alcohol use by 53 percent; not wearing a seat belt by 49 percent; lack of an air bag by 17 percent; no motorcycle helmet by 74 percent; no bicycle helmet by 39 percent. There were 153,168 lives saved by decreased drinking and driving, 129,297 by increased use of seat belts, 4,305 by increased air bag prevalence, 6,475 by increased use of motorcycle helmets, and 239 by increased use of bicycle helmets.

The researchers cite factors for the changes in the five behaviors over the 20-year period. Citizen groups that influenced attitudes and laws regarding drunken driving have been credited with part of this decrease. The first state seat belt law was adopted in 1984; by 2004, 80 percent of 52,000 observed front-seat motorists were belted, according to a survey by the National Highway Traffic Safety Administration. By 1994 most new cars had dual air bags, and these were required in cars by 1998 and in light trucks by 1999. Observed helmet use by motorcyclists was 63 percent in 1994, rose to 71 percent in 2000, but declined to 58 percent by 2002, according to a survey by the National Highway Traffic Safety Administration. Bicycle helmet use has become more common in some regions.

“While the rate of death attributed jointly to the five risk factors decreased by 48 percent, the rate of other deaths not attributed to these factors increased by 29 percent,” says Dr. Peter Cummings, a University of Washington  professor of epidemiology and principal investigator for the study. “This suggests that favorable changes in the prevalence of the risk factors we studied exerted a downward influence on crash mortality, while other changes increased crash mortality. One factor that may have increased crash mortality is faster driving speed; in 1987 many states raised the speed limit on rural freeways from 55 to 65 miles per hour, and after 1995 speed limits on many freeways were increased further. Another factor is the rise in miles driven, which increased from 6,885 per person-year in 1982 to 9,803 in 2001.1 A third factor may be the shift in the vehicle fleet from passenger cars to light pickups and sport utility vehicles.”

In addition to Cummings, the investigators are Dr. Frederick Rivara, a UW professor of pediatrics and adjunct professor of epidemiology; Dr. Carin Olson, a UW associate professor of medicine and adjunct associate professor of epidemiology; and Dr. Kathy Smith, an HIPRC investigator.

The study was supported by grants from the Centers for Disease Control and Prevention, and the Crash Injury Research and Engineering Network of the National Highway Traffic Safety Administration.