As state legislators across the United States enact laws that ban phoning and texting while driving, a new study is showing no reductions in crashes after hand-held phone bans take effect.

Comparing insurance claims for crash damage in 4 US jurisdictions before and after such bans, The Highway Loss Data Institute (HLDI) researchers find claim rates are comparable with nearby jurisdictions without such bans.

The laws aren't reducing crashes, even though we know that such laws have reduced hand-held phone use, and several studies have established that phoning while driving increases crash risk, says Adrian Lund, president of HLDI.

The HLDI compared collisions of 100 insured vehicles per year in New York, Washington D.C., Connecticut, and California -- all states with currently enacted roadway text bans.

Despite those laws, monthly fluctuations in crash rates didn't change after bans were enacted, all though there were less people using devices while driving.

An earlier study conducted by the HLDI reported that cellphone use was directly linked to four-fold increases in crash injuries. Also independent studies done by universities have shown correlation between driving while using a phone and crashes.

The link prompted the US government to draft a bill to prevent usage across the country, though it has not been ratified.

If crash risk increases with phone use and fewer drivers use phones where it's illegal to do so, we would expect to see a decrease in crashes, Lund says. But we aren't seeing it.

Lund believes that drivers in jurisdictions with such bans may be switching to hands-free phones which poses the same risks, he believes.

Whatever the reason, the key finding is that crashes aren't going down where hand-held phone use has been banned, Lund said.

The study comes as the U.S. Transportation Department prohibited texting by commercial drivers of interstate buses and trucks earlier this week.