Car Talk's
Driver Distraction Center
Produced in partnership with the University of Utah and University of Kansas

The Science of Distracted Driving

by Nathan John Medeiros-Ward
University of Utah Applied Cognition Laboratory

The odds of getting into a crash are 4 times higher when a driver is talking on the cell phone. To put the 4-fold increase in crashes in perspective, the odds of crashing are the same when driving drunk (at a blood alcohol level of .08 - the legal limit in all 50 US states). Simply put, driving while talking on a cell phone is like driving drunk (at least in terms of crash risk).

There is no safety advantage for hands-free cell phones (both hand-held and hands-free cell phones are associated with a 4-fold increase in the crash risk). Despite the laws in several states, research that has compared hand-held and hands-free cell phones does not find a safety advantage for one over the other.

The odds of crashing while texting are eight times higher than driving without distraction. That is twice the crash risk of a drunk driver (at a blood alcohol level of .08)! Drivers texting also have difficulty staying in their lane. The data indicate that if you text while driving, you will eventually cause a crash.

The brake reactions of a driver talking or texting on the phone are slower, increasing both the likelihood and severity of accidents.

Talking on a cell phone causes inattention blindness, where drivers look but fail to see things on the roadway. Drivers can fail to see up to half of the things that they would have seen had they not been talking on the phone. In fact, the brain activity for processing brake lights and traffic signals is cut in half when talking on a cell phone.

Carrying on a conversation with a passenger does not cause the kinds of impairments that we see with cell phone conversations. The passenger acts as another set of eyes and often adjusts their conversation as driving becomes more difficult. Passengers also help the driver by identifying hazards and helping the driver to navigate. On the whole, these helpful benefits of the passenger offset any costs of conversing.

For more information, visit the Applied Cognition Lab at the University of Utah.