SAN FRANCISCO, California, May 12, 2008 — The law requiring California drivers to use hands-free devices while talking on their mobile phones is likely to save hundreds of lives a year, particularly when the weather is bad or roads are wet, according to a new study released today by the Public Policy Institute of California (PPIC).
The study estimates that after the law takes effect on July 1st, California will experience 300 fewer traffic fatalities a year. The state currently logs more than 4,000 traffic deaths every year.
These findings differ from previous research that has questioned the effectiveness of hands-free laws in improving traffic safety.
Concern that phone use contributes to traffic collisions and fatalities has prompted many industrialized nations to require that drivers use hands-free technology while talking on the phone. In the United States, hands-free laws are in effect in New York, New Jersey, Connecticut, and the District of Columbia, as well as in several cities, including Chicago and Santa Fe, New Mexico. Washington state has a hands-free law that also takes effect on July 1st.
The PPIC study uses data collected at the state level on mobile phone ownership and traffic fatalities to analyze the effect of laws that mandate hands-free technology. The study finds:
- Mobile phone ownership appears to contribute to traffic deaths but only under certain driving conditions. If the weather is bad and the roads are wet, the effect is large. There is no observable effect in good weather or on dry roads.
- Laws requiring hands-free devices have reduced fatalities in adverse conditions by 30-60 percent, depending on how long the law has been in effect.
- Based on the experience of New York, which in 2001 became the first state to have a hands-free law, fatalities in adverse conditions may remain at a lower level several years after the law takes effect.
Previous research has found that drivers using hands-free phone devices were just as distracted as those using hand-held phones. These studies have relied on surveys of drivers, laboratory simulations, and observations in vehicles specially outfitted to record a driver’s behavior and distractions. However, studies using these approaches don’t help predict the effects of a hands-free law, says Jed Kolko, PPIC research fellow and author of the study.
“Mobile phone use can’t be measured accurately at the time of a traffic collision,” he says. “A driver may hang up to avoid looking negligent, and police can’t easily access mobile phone records.”
Laboratory simulations measure the effect of one kind of mobile phone device versus another. In other words, they measure distraction levels of a driver while using a phone.
“Drivers make real-time decisions that can’t be measured in a lab,” Kolko says. “They decide whether and when to use their phones. The question is how these laws might change drivers’ likelihood of using any mobile phone, whether it’s handheld or hands-free.”
It will take more years of data to understand how hands-free laws affect driver behavior, but Kolko suggests some possible explanations.
It may be that drivers find hands-free technology cumbersome and use their phones less often. Or they may shift their talking minutes to times when driving conditions are less hazardous. It’s also possible that the very fact of having such a law serves an educational function, a warning about the dangers of talking while driving.
Despite unanswered questions about how and why mobile phones affect traffic fatalities, the study’s results suggest strategies to guide public policy.
“Since the benefits of hands-free laws depend on driving conditions, it makes sense to more strongly enforce the laws when driving conditions are most difficult,” says Kolko. “That can save lives.”
The Public Policy Institute of California is a private, nonprofit organization dedicated to improving public policy in California through independent, objective, nonpartisan research on major economic, social, and political issues. The institute was established in 1994 with an endowment from William R. Hewlett.