From 1982 to 1997, American states got tough on impaired driving. Policies favored adopting lower blood alcohol concentration (BAC) limits for driving, administrative license revocation (ALR), and increased sanctions for those convicted of driving under the influence (DUI) of alcohol. In the absence of stricter laws, enforcement offers the greatest opportunity for reducing alcohol-impaired driving. A study of variations in DUI prevalence and several categories of enforcement intensity has found that the number of traffic stops and DUI arrests per capita had the most consistent and significant association with drinking and driving.
Results will be published in the January 2015 online-only issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.
"From 1982 to 1997, public attention to impaired driving was at its peak," said James C. Fell, a senior research scientist with the Pacific Institute for Research and Evaluation in Calverton, Maryland as well as corresponding author for the study. "Organizations such as Mothers Against Drunk Driving (MADD) and the Presidential Commission Against Drunk Driving (PCADD) were pressing the states to adopt tougher DUI laws. The minimum legal drinking age (MLDA) of 21 was passed by Congress and other effective laws were adopted in the states. By 1997, most states had already adopted laws on lower BAC limits as well as ALR."
"Impaired driving is clearly a major public health problem, associated with approximately 10,000 traffic crash fatalities each year," said Gregory Bloss, program director for economic and policy studies in the division of epidemiology and prevention research at the National Institute on Alcohol Abuse and Alcoholism. "Expanded public awareness of the dangers associated with drunk driving and various policy measures, including MLDA laws and .08 per se blood alcohol limits, have contributed to large reductions in alcohol-related traffic fatalities since the 1980s."
"Lowering the illegal BAC limit for driving from the current .08 to .05 and raising the drinking age to 25 would have a substantial general deterrent effect on impaired driving, but there is no indication, politically, that those measures will be adopted in this country," added Fell. "Most drunk driving legislation over the past 20 years has concerned sanctions for a DUI conviction. Our best strategy is to improve DUI enforcement of the current laws."
"Discerning the effects of enforcement efforts on these outcomes has been a notoriously difficult research problem," said Bloss. "A key stumbling block has been the lack of suitable data. This study makes an important contribution by pairing data on the prevalence of alcohol impairment among drivers from the National Roadside Survey (NRS) with multiple measures of enforcement effort."
Fell and his colleagues examined six different measures of enforcement intensity and their effect on the prevalence of weekend, night-time drivers in the 2007 National Roadside Survey who had been drinking alcohol and had BACs>.05 g/dL, as well as those who were driving with an illegal BAC>.08 g/dL.
"We found that two measures of enforcement intensity significantly affected the rate of impaired driving on the roads in a community: the rate of traffic stops and of DUI arrests," said Fell. "Communities with a high rate of traffic stops - representing enforcement visibility to the public - had a lower rate of impaired drivers on their roads. Similarly, communities with high rates of DUI arrests also had lower rates of alcohol-impaired drivers on their roads. This is the first study I am aware of that actually calculated several enforcement-intensity rates and related those measures to impaired driving on the roads in several communities."
"The central contribution of this study is to disentangle various elements of enforcement and compare how variation in their levels corresponds to variation in the prevalence of impaired and drinking drivers on the road," added Bloss. "Although this study is exploratory and its conclusions remain tentative, beginning to understand how different components of enforcement may help to change the prevalence of drunk driving is a step toward important practical information for law-enforcement agencies."
Both Fell and Bloss remarked that visible and publicized enforcement efforts in the form of increased numbers of police cars stopping drivers along roadways would lead to the perception that the chances of being caught are higher.
"The public notices police cars on the side of the road issuing citations or arresting drivers for DUI," said Fell. "That serves as a general deterrent and increases their perceived risk of being caught driving impaired."
"Given relatively severe penalties for impaired driving," added Bloss, "drivers who would be tempted to drive after drinking may be deterred by increases in the probability of detection, which may be directly related to the frequency with which they see flashing lights along the road. Although more research is needed, current findings suggest that greater intensity of general traffic enforcement during evenings and weekends when impaired driving is most prevalent may be an effective strategy to reduce the number of drinking drivers on the road."
"Alcohol researchers will need to conduct future research to determine what thresholds of enforcement intensity have a significant impact on alcohol impaired driving and on impaired driving crashes in communities," said Fell. "Our research gives the ranges of intensity; now we need the thresholds that make a difference. Furthermore, police agencies need to know how much they should increase their traffic stop rates or their DUI rates to really make a difference. What would happen in a community if the police increased their DUI arrest rate from 20 to 40 DUI arrests per 10,000 population? Would impaired driving decrease by a certain percent? How much of an increase in the rate would be needed? Policy makers and police agencies need these answers to determine if any increased enforcement would be cost effective."
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