Convicted drunken drivers in Sacramento County soon will have to convince their own cars they're sober before hitting the road.

Beginning July 1 in Sacramento and three other test counties, people convicted of first-time drunken-driving offenses must have ignition interlock devices – commonly known by the brand name Breathalyzer – installed in their vehicles for at least five months.

They'll have to blow into a tube, and if the device detects alcohol, the car won't start.

The pilot program is being hailed as a major step in California's decades-long efforts to cut drunken driving. Sacramento was included partly because of its high drunken-driving rate.

"By installing (the) devices, we are making it harder for DUI offenders to get behind the wheel while intoxicated, and we are working to save innocent lives," Gov. Arnold Schwarzenegger said after signing the bill.

Fourteen states have similar laws for first-time DUI offenders, said Laura Dean-Mooney, national president of Mothers Against Drunk Driving. "The great thing is, (offenders) can continue to drive to work or take their kids to school."

The program will be tested through 2015 in Sacramento, Alameda, Los Angeles and Tulare counties. A report to the Legislature in 2015 will evaluate whether it worked.

It takes effect despite opposition from some Orange County criminal defense attorneys and restaurant industry lobbyists, who say it should be reserved for serious repeat offenders.

"With this law, you are going to have the occasional drinker who had a half glass of wine too much" and who is unlikely to reoffend, said Ignacio Hernandez, a lobbyist for California DUI lawyers.

He warned the technology could have glitches that cause false positive readings.

DUI remains one of the state's top road concerns, safety officials said. In 2008, 30 percent of California roadway deaths – more than 1,000 – occurred in crashes where at least one driver was legally drunk, according to the state Office of Traffic Safety.

"We have a problem of enormous consequences in the state," said the ignition device law's author, Assemblyman Mike Feuer, D-Los Angeles.

In 2008, the city of Sacramento had the highest drunken-driving injury and fatality rate among the state's largest cities.

The law could affect about 4,700 first-time drunken drivers per year in Sacramento County, state data suggest.

A Department of Motor Vehicles analysis shows that 4 percent to 5 percent of first-time offenders in Sacramento are involved in a second DUI incident – either a crash or an arrest – within a year.

Under the new law, if the DUI conviction is a person's first, the driver must have the ignition interlock device installed for five months. A second offense would require 12 months, and a third 24 months. The law doesn't apply to motorcycles.

If the first-time conviction involved injury, the device must remain for a year.

Most drivers will have to pay for installation and monthly rental fees. Feuer estimated installation costs will be $75 or more, and monthly monitoring costs $50 or more.

Those fees will be reduced by up to 90 percent for lower-income offenders. That could cause some installers to balk rather than lose money by subsidizing the costs, said Taylor Reed of Ignition Interlock Service Centers of California.

"You are saying the guy can't afford $2.75 a day for (an ignition device), but he can afford to drive a car and spend enough to get drunk?" Reed said.

Feuer, however, said he doesn't expect problems with installation companies, based on the state's experience with a limited number of court-ordered ignition interlock devices now put in cars.

The DMV, which in 2004 reviewed studies from other states and countries, says such programs appear to reduce repeat offenses by anywhere from 40 percent to 95 percent while the devices are in place. Recidivism rates rise once they're removed.

Ignition interlock devices are not new in California. The state allows judges to require drunken drivers to use such systems, but data show that few do so.

In Sacramento, judges ordered the devices installed in only 3 percent of DUI cases they handled in 2007. Just a few of those were for first-time offenders.

Feuer and other advocates, including Mothers Against Drunk Driving, say technology has improved considerably since the devices came on the scene two decades ago.

Some require both blowing and inhaling, or humming, so that people can't cheat by using compressed air machines.

Of course, a person who has been drinking can still get a friend to illegally blow into the tube, enabling the car to start.

But such cheaters may not get far. Today's devices require drivers to retake the breath test at random moments while driving. If they fail to do so within the allotted time, the device will record the event as a failed sobriety test.

IGNITION INTERLOCK DEVICES CARRY PLENTY OF BACKUP CAPABILITIES

Answers to common questions about ignition interlock devices installed in vehicles (abbreviated from the Department of Motor Vehicles):

Can someone use a balloon or other air source to mimic human breath?

No. Devices can detect phony breath samples.

Can a driver have someone else take the breath test?

Yes, but it's illegal. Also, once the car starts, the device will randomly require a "running retest." The driver must pull over and retake the test within a given time period, or the unit will log a violation. With some devices, the horn will honk until the vehicle is turned off.

Will the ignition interlock unit lose all memory if the battery is disconnected?

No. There is a backup battery in the unit.

What happens if a driver misses a required device service appointment?

The device may enter a lockout condition and the driver will not be able to operate the vehicle.

What if the driver is taking a medicine or mouthwash with an alcohol base?

Alcohol-based products can register on the device.

What happens when a driver fails the device's test?

The device will enter a lockout period of a few minutes for the first failed test and a longer lockout for any subsequent failed test.

Can other people, such as a spouse, drive the vehicle?

Yes, but they must pass the device's test.

What happens if the vehicle stalls in traffic?

The device permits the driver to restart the vehicle without another breath sample, but a breath sample will be requested shortly after restarting.