Phoning while driving and texting behind the wheel are in the news. This is the highway safety issue of the moment, the subject of cartoons and, on a more serious side, the focus of legislation. A key question is whether such laws succeed in changing patterns of driver cell phone use.

Insurance Institute for Highway Safety (IIHS) researchers recently conducted a new round of observations of driver use of hand-held phones in three jurisdictions where the practice is banned. The findings, along with results of previous studies, reveal differing effects. In the District of Columbia, the proportion of drivers using hand-held phones dropped by about half immediately after a ban took effect in 2004. Nearly five years later use has edged up a little, but the decline is largely holding relative to nearby Virginia and Maryland.

The story is different in New York, the first U.S. state to prohibit drivers from using hand-held phones in 2001. Connecticut enacted a ban in 2005. Comparing trends in these states over time, researchers found immediate effects of both laws. Cell phone use declined an estimated 76 percent in Connecticut and 47 percent in New York. But then use began going back up.

To quantify the long-term effects, researchers observed phone use multiple times during 2001-09 in both the study states and nearby communities without phone bans. The purpose was to estimate the proportion of drivers expected to be using hand-held phones if the laws hadn't been enacted. By this measure, hand-held phone use was an estimated 65 percent lower in Connecticut, 24 percent lower in New York, and 43 lower in the District of Columbia than would have been expected without the laws.

In Connecticut and New York, phone use was higher in spring 2009 among women of all ages compared with men and higher among drivers younger than 25 versus 25-59 year-olds. Only 1 percent of drivers 60 and older were observed using phones.

"What's clear from the surveys, despite some variability in their findings, is that bans on hand-held phoning while driving can have big and long-term effects, but the safety implications still aren't clear," says Institute President Adrian Lund. "Many drivers still use their hand-held phones, even where it's banned, and other drivers simply switch to hands-free phones, which doesn't help because crash risk is about the same, regardless of phone type."

Two studies that rely on the cell phone records of crash-involved drivers show big increases in crash risk when drivers talk on phones, whether hands-free or hand-held. The risk of a crash involving injury or property damage is four times as high.

Other studies have been conducted on simulators. Virtually all of these confirm that phoning impairs driving performance, and the impairment is similar for hand-held and hands-free phones.

The crash risk is about the same, whether drivers use hand-held or hands-free phones, so if motorists respond to hand-held bans by switching the type of phone they use, they may not be reducing crash risk. What they're doing, though, is engaging in a practice that's harder to curb because laws against it are harder to enforce.

"Police officers can see whether a driver is holding a phone to the ear, but it's going to be much harder to determine if a driver is sending a text message or talking on a hands-free phone," Lund points out.

No U.S. state currently bans all drivers from using hands-free phones. Twenty-one states and the District of Columbia prohibit beginning drivers from using any type of phone, including hands-free.

For a copy of the full study, go to www.iihs.org.

The Insurance Institute for Highway Safety is an independent, nonprofit, scientific, and educational organization dedicated to reducing the losses - deaths, injuries, and property damage - from crashes on the nation's highways.