September 24, 2009

Study: Zero tolerance laws, zero effect

Zero alcohol tolerance laws for drivers under age 21 found guilty of drunken driving have zero effect, a U.S. researcher says.

Darren Grant of Sam Houston State University analyzed data from 30,000 vehicle fatalities in nighttime accidents involving drivers under age 21.

Both in terms of the number of accidents and the blood alcohol of the drivers in those accidents, the research consistently showed that zero tolerance laws had no effect, Grant said in a statement. Other factors matter, but not these laws.

The study, published in the journal Economic Inquiry, found that among drivers involved in traffic accidents, there is the same fraction of heavy drinkers, the same fraction of mild drinkers, the same fraction of nondrinkers.

Grant also compared the blood alcohol distributions of involved drivers in the two years before zero tolerance laws were established in each state, and again in the two years after.

The two distributions were also virtually identical, Grant said. That's a sign that this law is essentially inert; if it's affecting the amount of drinking that people do, these distributions should look different.