Convicted drunken drivers in four California counties will have to prove they haven't had a drink before they can start their vehicles, under one of several laws taking effect Thursday.

The law requires first-time and repeat offenders to install ignition interlock devices in their vehicles. If the device detects alcohol on the driver's breath, the vehicle will not start.

The law can "save hundreds of lives here," said Assemblyman Mike Feuer, D-Los Angeles. "This is a piece of legislation that will really matter at the community level."

The law starts on an experimental basis in four counties - Alameda, Los Angeles, Sacramento and Tulare. The experiment phase will last five years, after which lawmakers can consider expanding the program statewide.

J.T. Griffin, vice president of public policy for Mothers Against Drunk Driving, said he hopes the program will be expanded and serve as a model beyond the 13 states that already require offenders to use interlock devices.

The device consists of a breathing tube, a device that measures alcohol content and a connection to the ignition system. Drivers must blow into the tube before starting the vehicle and periodically must stop to retake the test while they are traveling. The device keeps track of failed tests.

Most offenders will be required to pay about $125 to install and $60 monthly to maintain the device, although there is a program for low-income convicts, said Mike Marando, a spokesman for the California Department of Motor Vehicles. The DMV also will collect a one-time $45 administration fee.

First-time offenders will be required to have the devices installed for five months. A second DUI extends the requirement to 12 months, a third offense to 24 months and a fourth conviction to 36 months. The time periods double if the offense results in an injury.

There is no limit in California on the number of DUI convictions drivers can have before losing their licenses, according to the DMV.

Marando cited a study by the International Council on Alcohol, Drugs and Traffic Safety, which found a 40 percent to 95 percent reduction in the rate of repeat drunken driving offenses while the devices were installed. Violations increased once they were removed.

Joshua Dale, executive director of the California DUI Lawyers Association, said the state would get better results by targeting young or repeat offenders rather than imposing a blanket burden on all DUI offenders. Many first-time offenders learn their lesson and never drive drunk again, he said.

Dale said many drivers will be unable to afford the devices, on top of the typical $2,500 they pay in fines and court fees.

Griffin, who works at MADD's office in Washington, D.C., said requiring the devices is less onerous than prohibiting offenders from driving.

"The interlock device lets them go to work, go to school, go anywhere they want to go. It just requires them to go sober," he said.