Cellphone Bans May Not Prevent Accidents

Casey B. Mulligan is an economics professor at the University of Chicago. He is the author of “The Redistribution Recession: How Labor Market Distortions Contracted the Economy.”

A new study has found that cellphone bans have little effect on accident rates, even though they do affect driving habits.

Every year people are killed in car crashes, and in many of those accidents a driver was using a cellphone. For this reason, many states prohibit drivers from texting while driving or from holding cellphones in their hands.

The National Highway Traffic Safety Administration’s National Occupant Protection Use Survey has been measuring driving habits for a couple of decades. The agency puts hidden observers at various stop signs and stoplights to watch the vehicles that drive by and record whether drivers are visibly using cellphones.

A recent study by Cheng Cheng, a graduate student in economics at Texas A&M University, uses the agency data to estimate the effect of cellphone bans on driver behavior. Because states adopt their laws at different times and some states have not yet adopted bans, Mr. Cheng is able to compare driver behavior trends across states in order to estimate effects of the new laws. He finds that visible cellphone use drops about 50 percent when a state begins its ban.

Simply put, driving habits change when states ban cellphone use, which means that drivers perceive that the new laws will be enforced and fines levied.

But it’s less clear whether their transformed behavior prevents accidents.

Using a separate quarterly data source on automobile accidents by state, Mr. Cheng investigates accident trends and their relationship to the cellphone bans. He finds no evidence that bans on texting affect accidents, and that his data “suggests that handheld bans might not reduce accidents.”

Mr. Cheng suggests that part of the population may drive more safely when the cellphone bans are in place, but that their safety records are offset by more dangerous driving by people who try to keep their cellphone use concealed from observers (especially, police officers). Or possibly drivers using cellphones drive more slowly because they know that they’re distracted, and the slower speeds offset the extra danger of driving while distracted.

Or perhaps lawmakers overestimated the benefits of regulating this sort of driver behavior.