Maneuvering through traffic while talking on the phone increases the likelihood of an accident five-fold and is actually more dangerous than driving drunk, U.S. researchers report.

That finding held true whether the driver was holding a cell phone or using a hands-free device, the researchers noted.

"As a society, we have agreed on not tolerating the risk associated with drunk driving," said researcher Frank Drews, an assistant professor of psychology at the University of Utah. "This study shows us that somebody who is conversing on a cell phone is exposing him or herself and others to a similar risk -- cell phones actually are a higher risk," he said.

His team's report appears in the summer issue of the journal Human Factors.

In the study, 40 people followed a pace car along a prescribed course, using a driving simulator. Some people drove while talking on a cell phone, others navigated while drunk (meaning their blood-alcohol limit matched the legal limit of 0.08 percent), and others drove with no such distractions or impairments.

"We found an increased accident rate when people were conversing on the cell phone," Drews said. Drivers on cell phones were 5.36 times more likely to get in an accident than non-distracted drivers, the researchers found.

The phone users fared even worse than the inebriated, the Utah team found. There were three accidents among those talking on cell phones -- all of them involving a rear-ending of the pace car. In contrast, there were no accidents recorded among participants who were drunk, or the sober, cell-phone-free group.

The bottom line: Cell-phone use was linked to "a significant increase in the accident rate," Drews said.

He said there was a difference between the behaviors of drunk drivers and those who were talking on the phone. Drunk drivers tended to be aggressive, while those talking on the phone were more sluggish, Drews said.

In addition, the researchers found talking on the cell phone reduce reaction time by 9 percent in terms of braking and 19 percent in terms of picking up speed after braking. "This is significant, because it has an impact on traffic as a system," Drews said. "If we have drivers who are taking a lot of time in accelerating once having slowed down, the overall flow of traffic is dramatically reduced," he said.

In response to safety concerns, some states have outlawed the use of hand-held cell phones while driving. But that type of legislation may not be effective, because the Utah researchers found no difference in driver performance whether the driver was holding the phone or talking on a hands-free model.

"We have seen again and again that there is no difference between hands-free and hand-held devices," Drews said. "The problem is the conversation," he added.

According to Drews, drivers talking on the phone are paying attention to the conversation -- not their driving. "Drivers are not perceiving the driving environment," he said. "We found 50 percent of the visual information wasn't processed at all -- this could be a red light. This increases the risk of getting into an accident dramatically," he said.

The reason that there aren't more accidents linked to cell phone use is probably due to the reactions of other -- more alert -- drivers, Drews said. "Currently, our system seems to be able to handle 8 percent of cell-phone drivers, because other drivers are paying attention," he said. "They are compensating for the errors these drivers are causing," he speculated.

This is a growing public health problem, Drews said. As more people are talking and driving, the accident rate will go up, he said.

One expert agreed that driving and cell phone use can be a deadly mix.

"We don't believe talking on a cell phone while driving is safe," said Rae Tyson, a spokesman for the U.S. National Highway Traffic Safety Administration (NHTSA). "It is a level of distraction that can affect your driving performance," he said.

NHTSA has just completed a study that showed that 75 percent of all traffic accidents were preceded by some type of driver distraction, Tyson said.

Tyson pointed out that talking on the phone is very different than talking to the person in the passenger seat. "If you are engaged in a conversation with a passenger, the passenger has some situational awareness, whereas a person on the phone has no idea what you are dealing with on the road," he said.

"Our recommendation is that you should not talk on the phone while driving, whether it's a hand-held or hand-free device," Tyson said. "We realize that a lot of people believe that they can multi-task, and in a lot of situations they probably can, but it's that moment when you need your full attention, and it's not there because you are busy talking, that you increase the likelihood that you are going to be involved in a crash," he said.

Tyson also sees this as a growing public health issue. "Every time we do a survey, there are more people using cell phones while driving," he said. "And the popularity of hand-held devices like Palm Pilots or Blackberries, and people using them in the car, is another problem," he added.

An industry spokesman said cell phones don't cause accidents, people do.

"If cell phones were truly the culprit some studies make them out to be, it's only logical that we'd see a huge spike in the number of accidents [since their introduction]," said John Walls, a vice president at the industry group, the Cellular Telecommunications & Internet Association-The Wireless Association. "To the contrary, we've experienced a decline in accidents, and an even more impressive decline in the accident rate per million miles driven," he said.

"We believe educating drivers on how to best handle all of the possible distractions when you're behind the wheel is the most effective means to make better drivers, and that legislation focusing on a specific behavior falls short of that well-intended goal and creates a false sense of security," Walls said.