Almost everybody agrees that driving while engrossed in a cell phone conversation or while text messaging is a really bad idea. Even folks who do it regularly know better.

But preventing people from doing it isnt easy.

And, surprise, a recently released study by the Highway Loss Data Institute and the Insurance Institute for Highway Safety, found there was no significant reduction in accident claims in states that have banned the use of hand-held cellphones behind the wheel.

The study finding is the reverse of those studies that confirm what everybody expected, or believed they knew.

In New York state, for example, the legislature forbade motorists to use handheld mobile phones while driving in November 2001. Driver phone use fell by an estimated 47 percent, the HLDI/IIHS study found.

Yet, while monthly collision claims in New York did show a decline after the ban, that drop had actually begun before the ban was enacted.

In California, a handheld cellphone ban became law in July 2008. But HLDI said "no notable change was apparent" because of the ban.

Likewise, Connecticut and Washington, D.C., didn't show a significant change in accident claims after their bans, or compared to other states that had no cellphone bans.

Some in the safety community say the failure to see lower crash rates suggests stronger enforcement is needed. Others suggest the ban on holding a phone doesn't attack the real problem, which is the distraction of talking to someone who's not in the car.

The studys results could give ammunition to those who say that future legislation or regulation on distracted driving needs to have a broader focus than just holding a handset.

For example, the Governors Highway Safety Association recommends adopting bans on texting but holding off on cellphone bans because theres just "too much conflicting data."

Other highway safety experts worry that the study could cause people to downplay the need to curb cellphone use while driving.

The U.S. Department of Transportation, in a statement, said that "it is irresponsible to suggest that laws banning cellphone use while driving have zero effect on the number of crashes on our nation's roadways."

The USDOT points to a National Safety Council estimate that drivers talking on cellphones cause 1.4 million crashes a year, and driving while texting is responsible for a "minimum of 200,000 additional crashes" a year.

In New York state, a spokeswoman with the Department of Motor Vehicles said "distracted driving contributes to one in five crashes." The effort to use laws and enforcement to change behavior is just beginning, she added.

But Adrian Lund, president of the Insurance Institute for Highway Safety, says the institute has pointed out for some time that even as cellphone use exploded over the years, highway accident rates haven't risen in parallel.

That surprises many because observations of drivers suggest that the risk that someone using a cellphone behind the wheel will get into an accident is about four times higher than the risk for someone not using a phone.

That risk, Lund says, is about the same whether the driver holds the phone or uses a hands-free setup.