It is an open question whether roadside sobriety checkpoints, also known as DUI roadblocks, are an effective use of police resources in stopping drunk drivers.
DUI roadblocks are pre-announced events where police details stop drivers and check for driver impairment or other problems. Under California law, there are strict procedures for allowing these checkpoints. They must be announced in advance, and drivers must be selected to be stopped in a completely unbiased way.
Critics of these roadblocks like the American Beverage Institute, a restaurant industry lobbying group, point to evidence that these details are costly, inefficient, and a poor use of resources compared to roving police patrols. The rate of people actually found to be drunk via these checkpoints is incredibly tiny.
And that makes a lot of sense, logically. Should police be spending their time selected people to stop at random, or should they be out aggressively patrolling, looking for suspicious and dangerous driving activity that may be evidence of impairment and drunk driving.
But the police roadblocks are popular with MADD and some citizens who favor aggressive police tactics, whether or not they are efficient at their stated purpose.
Police patrol-hours are a limited resource. In principle, everyone probably agrees that police should be doing the most productive activity they can, to protect public safety. And there really is ample evidence to suggest that stopping people at random looking for violations is not very useful compared to other activities, like active patrolling.
But it is a legitimate question as to why lobbyists in the alcohol-serving industry would be inclined to spend time and effort protesting these DUI checkpoints nationwide. And why federal money is often used to pay for these efforts.
The answer to both may be that these roadblocks serve as a deterrent to drunk drivers. Knowing that the roadblocks are regularly deployed in certain areas may have the effect of making people more careful about their alcohol consumption if they know they are driving home.
And less alcohol served is bad for business for the American Beverage Institute’s clients.
It is always hard to measure a deterrent. To measure the cause of something that didn’t happen, you have to somehow isolate and account for any other causes or influences other that the one you are trying to measure.
But given the interest in DUI roadblocks from all sides, it is reasonable to guess that both law enforcement and the alcohol-entertainment industry suspect they are a deterrent to drinking and drunk driving.