This study examines the correlation between the seriousness of injuries caused by vehicle accidents and the blood alcohol level in drivers. The 1,495,667 accidents that occurred in the U.S. between 1994 and 2008 were assessed for their seriousness and the alcohol levels in the driver’s blood. It was found that drivers with considerably low alcohol levels in their blood were also prone to serious accidents when compared to sober drivers. They were liable to drive faster, disregard seat belt safety, and were more likely to be driving the striking vehicle. This study found that the chances of fatal accidents were high even when the alcohol levels in blood were far below the current permissible limit of 0.08 percent in the U.S. Thus, the legal limit of blood alcohol level should be reduced to prevent fatal motor vehicle accidents in the future.

Previous laboratory tests show that blood alcohol levels as low as 0.03 percent can affect cognitive functions, causing inability to perform tasks that require alertness and immediate response. According to the authors of this study, laboratory tests have their own limitations, and a true estimate of the permissible levels of blood alcohol level can only be made through epidemiological studies of fatal vehicle accidents. The legal blood alcohol levels for a driver vary widely across the world and even within the different states in the U.S. The permissible level in Sweden is 0.02 percent, while Germany, Japan, and the U.S. have set the legal limit as 0.05, 0.03 and 0.08 percent, respectively. Such a wide variation in the legal blood alcohol limit raises doubts over its efficacy. Thus, the researchers in this study analyzed previously reported cases of fatal road accidents, in order to estimate the appropriate blood alcohol limit that can ensure road safety.

* Data from the Fatality Analysis Reporting System (FARS) in the U.S. was analyzed for automotive vehicle accidents from 1994 to 2008. A total of 1,495,667 cases were studied.
* The accidents took place at all hours and involved at least one death. Blood alcohol levels in increments of 0.01 percent were recorded.
* Use of seatbelt, speed of the vehicle, areas of accidents, injuries, and the number of people involved in each accident were noted. The drivers’ blood alcohol levels, signs of tiredness and negligence were also recorded.
* Severity of the accident was calculated as a ratio of serious injury (incapacitating or fatal) for a particular alcohol level to non-serious injury (none or possible injury) for the same.

* The seriousness factor (serious injury versus non-serious injury) was significantly higher for drivers with a blood alcohol level of 0.01 percent, as opposed to sober drivers with a blood alcohol level of 0.0 percent.
* The seriousness factor increased consistently and significantly with a 0.01 percent increase in blood alcohol level.
* The severity of injuries was more for those inside the vehicle than those outside it (pedestrians and bystanders).
* The seriousness factor for drivers’ injuries increased significantly for those with 0.01 percent blood alcohol level. Injuries to the driver were considerably more severe than to the passengers.

Shortcomings/Next steps
Due to limitations of the available data, this study could analyze only accidents with fatalities. According to the authors of this study, the severity of injuries calculated as the seriousness factor (S) is based on accidents that have already occurred. It cannot indicate the chances of an accident that is yet to occur, based on how many miles the driver drove under the influence of alcohol.

Automotive accidents are common in the US. About 50,430 vehicles were involved in accidents in 2008, causing 37,261 fatalities and 10,048 cases with disabilities. Drunken driving is a major cause of vehicle accidents. Unlike Japan and many European countries, where very low levels of blood alcohol are permitted, the legal limit in U.S. is considerably higher, at 0.08 percent. After considering factors that may affect fatalities in an accident (age of the vehicle, seat belts, speed, etc.), the researchers of this study conclude that drivers with higher alcohol levels are more prone to ignore common safety practices. The current U.S. blood alcohol level limit of 0.08 percent needs to be reduced to the levels permitted in Japan and Sweden, in order to avoid future vehicle accidents and serious injuries and the costs associated with them.

For More Information:
The Relationship between Serious Injury and Blood Alcohol Concentration (BAC) in Fatal Motor Vehicle Accidents
Publication Journal: Addiction, June 2011
By David P. Phillips; Kimberly M. Brewer; Department of Sociology, University of California at San Diego

*FYI Living Lab Reports Are Summaries of the Original Research.