More than 250 bills prohibiting or restricting cellphone use while driving are pending in 42 state legislatures despite disagreement over the risks cellphones pose and the effectiveness of enforcement.

The number is up from about 120 bills in just 18 states 10 months ago, according to an analysis by the Insurance Institute for Highway Safety, a safety research group funded by insurers. Four states — Georgia, Idaho, North Carolina and Texas — are considering banning all types of cellphone usage behind the wheel, including hands-free devices.

Watching that legislation are wireless carriers and automakers, which have invested millions of dollars in hands-free technology built into vehicles. At least one insurer is also taking action: Nationwide will soon offer discounts to parents who buy technology that disables their teens' phones while their vehicles are in motion.

Six states plus the District of Columbia currently ban handheld cellphone use while driving. Legislators in 23 states have introduced bills to allow only hands-free phoning.

At the end of 2008, CTIA-The Wireless Association estimated that 270 million people — about 90% of the U.S. population — had cellphones. The latest data available from the National Highway Traffic Safety Administration estimated that in 2007, about 11% of the population at any moment during the day used a phone while driving.

Some of the legislative activity was prompted by the National Safety Council, which in January declared hands-free calling as dangerous as holding a phone. John Ulczycki, its vice president of research, communication and advocacy, says he's been meeting with state officials for several weeks encouraging them to introduce bills banning all forms of in-car cellphone use other than emergency calls. The group, funded by more than 20,000 companies, hopes to persuade Congress to offer financial incentives to states that pass such laws.

"When our friends have been drinking, we take the car keys away," says Janet Froetscher, CEO of the safety council. "It's time to take the cellphone away."

The tough talk is despite disagreement over cellphone risks by leading academic and industry researchers. "Unlike with seat belt and drunk-driving legislation, there's no consensus as to what an effective cellphone law entails and also no evidence that these ... approaches have any impact," says Barbara Harsha of the Governors Highway Safety Association.

Copyright 2008 USA TODAY, a division of Gannett Co. Inc.