NEW YORK (CNNMoney.com) -- State laws that ban drivers from talking on hand-held cell phones seem to have no effect on crash rates, according to a study released Friday.
The Highway Loss Data Institute compared collisions of 100 insured vehicles per year in four different jurisdictions before and after bans on handheld cell phone use took effect. The study was done in New York, Washington, D.C., Connecticut and California.
Data were also collected from nearby states for comparison.
Monthly fluctuations in crash rates didn't change after bans were enacted, the study found. Crash rates compared to nearby places without handheld phone bans also didn't change.
Earlier studies by the Institute, which is funded by insurance companies, found four-fold increases in injury-related crash risk associated with cell phone use, so this result was surprising. Surveys of driver behavior following bans raised more eyebrows. They showed actual reduction in cell phone use, the Institute said.
"We're currently gathering data to figure out this mismatch," said Institute President Adrian Lund.
One possible reason, Lund suggested, is that drivers are simply switching to hands-free phone use. Still, some studies suggest that the risk of hands-free phone use while driving is little different from handheld phone use.
Institute spokesman Russ Rader suggested that laws attacking particular types of distraction may be ineffective because there are simply too many distractions available to drivers for laws dealing with just one to have much impact.
"Whatever the reason, the key finding is that crashes aren't going down where hand-held phone use has been banned," Lund points out. "This finding doesn't augur well for any safety payoff from all the new laws that ban phone use and texting while driving."
Iran could be pumping more than four million barrels of oil a day by the end of 2016, the country's oil minister tells CNN in an exclusive interview. More
Intel's new sixth-generation Core processors double performance over the past generation. More
Here's what you need to earn to afford a home in the 27 biggest metro areas in the country, according to HSH.com. More