Though drivers tend to think otherwise, there is no evidence that using a hands-free cellphone device behind the wheel is any safer, according to a report compiled for the Swedish government.

“Mobile phone conversations during driving have a negative impact on driving performance regardless of whether a hand-held or a hands-free phone is used,” the report by the Swedish National Road and Transport Research Institute. “Phone conversations lead to longer reaction times. This is the case regardless of phone type.

The institute drew on an emerging body of research in Europe and the United States from laboratory testing of reaction times and crash statistics. Several earlier studies have shown that drivers are equally distracted by conversation with a hand-held and a hands-free cellphone.

The District, Maryland and eight other states require drivers to use hands-free devices. Thirty-four states, including Virginia and Maryland, and the District have laws that ban the sending and receiving of text messages while driving.

“Some studies suggest that drivers adjust their speed and headway when using a hand-held phone, but not when using a hands-free phone,” the new report said.

“This may indicate that drivers compensate for the deteriorating effects of mobile phone use when using a hand-held phone but neglect to do so when using a hands-free phone, possibly because a hand-held phone serves as a reminder of being engaged in something else than driving.”

The Swedish researchers also said that a review of mobile phone use at the time drivers were involved in a crash showed that hands-free phone offered no safety advantage.

“Many drivers think that it is safer to use a hands-free set than a hand-held telephone, but this has not been confirmed by the available research,” their report said.

The National Highway Traffic Safety Administration says that 5,474 people were killed and an estimated 448,000 were injured in 2009 in accidents that involved distracted driving. NHTSA said that accounted for about 16 percent of all traffic deaths.