“At the end of the day, the average person's commute is longer because of that person who is on the cell phone right in front of them,” says Dave Strayer, a University of Utah psychology professor and leader of the research team.
“If you talk on the phone while you're driving, it's going to take you longer to get from point A to point B,” says Joel Cooper, a doctoral student in psychology, “and it's going to slow down everybody else on the road.”
Cooper is scheduled to present the study in Washington, D.C., on Wednesday, Jan. 16, during the Transportation Research Board's annual meeting. The board is part of the National Academies, parent organization of the National Academy of Sciences, National Academy of Engineering and Institute of Medicine.
In recent years, Strayer's research group has published studies showing that:
* Hands-free cell phones are no less dangerous while driving than hand-held cell phones because the conversation itself is the major distraction.
* When young adults talk on cell phones while driving, their reaction times become as slow as reaction times for senior citizens.
* Drivers talking on cell phones are as impaired as drivers with the 0.08 percent blood alcohol level that defines drunken driving in most states.
* Highway statistics suggest drivers on cell phones are four times more likely to be in accidents, and Strayer's earlier research suggests the risk is 5.36 times greater.
The Cellular Telecommunications and Internet Association claims 240 million U.S. subscribers in a nation of 303 million people. An insurance company survey estimated 73 percent of wireless users talk while driving. Another survey found that during any given daytime moment, 10 percent of U.S. drivers are using cellular phones.
The researchers note that 50 countries have adopted laws banning hand-held phones while driving. But they say hands-free phone conversations are distracting as well, “thus, the majority of current regulation appears to be misguided.”
How the New Study was Conducted
Earlier studies found that cell phone users follow at greater distances, are slower to hit the brakes, and are slower to regain speed after braking. But such research didn't examine how traffic efficiency is influenced by individual cell phone users.
The new study used a PatrolSim driving simulator, in which a person sits in a front seat equipped with gas pedal, brakes, steering, and displays from a Ford Crown Victoria patrol car. Realistic traffic scenes are projected on three screens around the driver.
The new study involved 36 University of Utah psychology undergraduates. Each student drove through six 9.2-mile-long freeway scenarios – two each in low-, medium-, and high-density traffic, corresponding to freeway speeds of 70 mph to 40 mph. Each 9.2-mile drive included 3.9 miles with two lanes in each direction and 5.3 miles with three lanes each way. Traffic speed and flow mimicked Interstate 15 in Salt Lake City.
Each student spoke on a hands-free cell phone during one drive at each level of traffic density and did not use a cell phone during the other three drives. A volunteer on the other end of the phone was told to maintain a constant exchange of conversation.
The drivers were told to obey the 65-mph speed limit and to use turn signals. That let participants decide their own speeds, following distances, and lane changes.
“We designed the study so that traffic would periodically slow in one lane and the other lane would periodically free up,” Cooper says. “It created a situation where progress down the road was clearly impeded by slower moving vehicles, and a driver would benefit by moving to the faster lane, whether it w