At 70 mph, this half-second difference is equivalent to traveling an additional 46 feet before reacting to a road hazard, researchers said.

The effects were not as significant with hands-free phone use, tests showed.

British Ban Pending

"There has been a lot of attention paid to driving while using a mobile phone, and we wanted to quantify the risk by using drunk driving as a benchmark to establish the danger," Dominic Burch, road safety campaign manager for Direct Line, told Wireless NewsFactor.

Burch said the data support legislation currently under consideration by Parliament to ban handheld mobile phone use by drivers in Britain.

"It's similar to the bill passed in New York State and in other countries and would make this a specific offense under our law," he said.

Burch said Direct Line commissioned the TRL research following a recent survey done by the company showing that four out of 10 drivers, or about 10 million UK motorists, said they have used a mobile phone behind the wheel.

"We were surprised by the results." Burch said the researchers expected that alcohol consumption would cause greater impairment of driving ability than talking on a mobile phone. "We would like to see the use of mobile phones when driving, both handsheld and hands-free, become as socially unacceptable as drunk driving," he added.

Burch emphasized that the results are not meant to encourage drinking and driving, but that mobile phone use is a serious distraction.

Chuck Eger, director of the office of driver safety at Motorola, said that while he had not seen the Direct Line study, he questioned its conclusions.

"Based on the work in this area to date that has been conducted by experts in the field in the U.S., it's premature to reach a definitive conclusion on what is safe and what is not safe regarding telecommunications in cars," he told Wireless NewsFactor.

Eger noted that when driver distractions are ranked in studies, the use of cell phones is typically low on the list. "This study has no comparison distractions to offer," he said.

"Our goal is to educate our customers; they need to use good judgdment in deciding when it is appropriate to make a call while driving and when it is not appropriate," Eger said.

Debate Rages On

The U.S. National Safety Council used a driving simulator in a study similar to the British study and found that talking on either a handheld or hands-free cell phone led to "significant" distractions for drivers.

For its part, General Motors (NYSE: GM) last year issued a study saying that only two of the 8.1 million embedded cell phone calls placed to GM's OnStar call center advisor from October 1996 (when the OnStar telematics system was introduced) through May 2000 came from drivers known to be on the phone at the time of a crash severe enough to deploy vehicle air bags.

There was no evidence that the calls actively contributed to the crashes, GM said, pointing out that an examination of its records showed other contributing factors were at play in both accidents.

Outside the Car

In May 2001, the American Automobile Assocation (AAA) released the results of a study funded by the AAA Foundation for Traffic Safety showing that drivers involved in serious crashes most often were distracted by something outside their vehicle (29.4 percent), while cell phone use contributed to just 1.5 percent of such incidents.

The AAA results have drawn fire for the study's methodology, primarily because they rely only on those accidents reported by drivers and because the estimates for cell phone use are based on just 42 reported cases.