Previous studies have found that drivers talking on cell phones are up to four times as likely to be involved in an accident, the same risk as driving while drunk.
Fifty countries now have laws prohibiting the use of cell phones while driving, unless those phones are hands-free. Even then, the research isn't clear that hands-free devices help reduce driver distraction.
Earlier studies have found that cell phone users follow other cars at greater distances, are slower to hit the brakes and slower to regain speed after braking.
For this study, 36 University of Utah psychology undergraduate students used a PatrolSim driving simulator, built to mimic a Ford Crown Victoria sedan with automatic transmission. Different traffic scenarios appeared on three screens around the driver.
Each participant drove through six, 9.2-mile-long stretches of highway: two each in low-, medium- and high-density traffic with freeway speeds of 70 mph to 40 mph. One ride at each density level was done while talking on a cell phone and one while not using a cell phone.
"We found that when drivers were conversing on the cell phone, they drove those sections about two miles per hour slower when traffic density was medium or high," Cooper reported. "In all three scenarios, when people were talking on the cell phone, they made about 20 percent fewer lane changes."
Cell phone talkers took 15 seconds to 19 seconds longer to complete the distance assigned, and they also took 17 percent more time to recover half of their speed after braking. Motorists on cell phones also tended to trail other cars rather than overtake and pass them, potentially adding to traffic slowdowns.
All of this came from a simulation involving only one person talking on the phone.
"The next step is to take these, plug them into the microsimulator and try to make some more concrete generalizations about broad traffic flow," Coope
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