Back when you learned to drive, you may have been instructed to keep your hands on the wheel at 10 o'clock and 2 o'clock. Of course, the older you got, the more likely that rule was relegated to the realm of "suggestion," especially as the equipment in our cars--stereos, onboard navigation, even climate control--got more and more complicated. And of course, there's the all too common sight today of someone speeding past you while chatting merrily away on his or her cell phone.

But if you're a California resident, it's time to hang up and drive. As of Tuesday, most drivers in the Golden State are prohibited from talking on their cell phone while driving unless they're using a handsfree device, such as a Bluetooth headset.

The law aims to reduce the number of accidents that occur because people are distracted while talking on the phone, which some reports contend can be as dangerous as driving while intoxicated. Californians pulled over while using their cell phones without a handsfree device will receive a $20 fine the first time; the fine jumps to $50 for subsequent infractions.

There are some exceptions to the California law. Emergency personnel driving authorized vehicles in the course of their duties are exempt, as are commercial drivers (those with Class A or B licenses), though only until 2011.

Five other states--Connecticut, New York, New Jersey, Utah, and Washington (whose law also went into effect Tuesday)--currently ban handheld cell phone use while driving; Washington D.C. and the U.S. Virgin Islands have bans as well. Illinois, Ohio, New Mexico, Massachusetts, Michigan, and Pennsylvania have no statewide laws, but allow local jurisdictions to enforce restrictions at their own discretion, resulting in bans in cities such as Chicago, Cleveland, Santa Fe, and Albuquerque. In addition, New Mexico bans the use of cell phones while driving in state vehicles.

Several states have tried and failed to ban cell phones while driving, including Arizona, Kansas, Maryland, Nevada, Oklahoma, West Virginia, Wisconsin, and Wyoming. Others, such as Hawaii, Indiana, Nebraska, North Dakota and Texas, are still debating legislation. And a number of countries outside the U.S. have also enacted restrictions on the practice.

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