Alcohol-related traffic crashes are not necessarily caused by alcohol. Many are, but no one knows the exact proportion. So what’s the role of alcohol as a cause of traffic crashes?

First, there’s very strong facts of two important things.

1. 1. Alcohol adversely affects driving-related skills. That’s such things as vision, reaction time, judgment, and the ability to divide attention.
   2. Intoxication greatly decreases driving performance.

Crashers are Similar

It is also clear that drinking drivers who crash are similar in many ways to sober drivers who crash. Both groups are disproportionately

• • Young
  • Male
  • Single
  • Suffer from alcohol or drug problems
  • Characterized by aggression, hostility or and other traits.

Drunk drivers don’t become model drivers when sober. Even when completely sober, those who sometimes drive drunk are at high risk of being involved in traffic crashes. But there’s every reason to believe that alcohol often contributes to crashes.

Responsibility Analysis

One technique that shows this is called responsibility analysis. Resarchers examine multiple-vehicle crash reports without knowing the drivers’ blood alcohol contents (BACs). Then they estimate the degree to which each driver was responsible for the crash.

In a sample of injured drivers, they estimated that 34-43% of sober drivers were responsible. That compared to 74-90% of drunk drivers.¹

A large study studied 1,882 killed drivers in several states. It concluded that 68% of sober drivers and 94% of drunk drivers were responsible for the crashes. The responsibility rates were higher in this study. That’s because it included single vehicle crashes. And drivers in single vehicle crashes are almost always deemed responsible. But the pattern is the same. That is, responsibility for crashes increases with intoxication.²

Important Question

How many drunk drivers would have had accidents if they were sober? Again, no one knows. But one expert, James Hedlund, has identified three broad types of drinking drivers. The answer may differ for each.

1. 1. “Normal” drivers who are social drinkers. Such drivers may miscalculate the effects of alcohol on their performance. Obviously alcohol increases their crash risk. Clearly, their crash rates would drop if they did not drive after drinking,
   2. “High-risk” drivers. These are drinkers for whom alcohol abuse may just be another form of risk-taking. Or may promote this behavior by lowering inhibitions. Abstaining might not reduce their crash rates much.
   3. Alcoholics, for whom alcohol abuse is an important part of life. Abstaining would require a complete lifestyle change. If they abstained, their crash rates should drop greatly.³

Groups Respond Differently

Dr. Hedlund says measures to limit drinking and driving effect the three groups differently.

1. 1. Arrest, fines, shame, etc. tend to be effective in reducing violations by “normal” drinkers. Education may also be effective with this group. In fact, much of the reduction in alcohol-related crashes may come from this group.
   2. Arrest and punishment may have little effect on “high-risk” drivers. Some drivers may mature out of high-risk behaviors. But high-risk drivers may be the hardest to change. That’s because the desire for high-risk may be so deeply rooted in their personality.
   3. Alcoholics are not likely to be effected by anything not dealing directly with their alcoholism. So they are most likely to be changed by DUI Courts.

The proportion of alcohol-involved traffic accidents that would have occurred even if the drivers had been sober remains unknown.