In the fight against drunk driving, states are splitting into two groups. They disagree over the best way to discourage convicted drunk drivers from driving drunk again and, in the process, are raising questions about the effectiveness of ignition interlocks. Now, after years of state lawmakers choosing sides, Congress will get involved too.

The disagreements come a decade after all states adopted laws making it a crime to drive with a blood alcohol content of .08 or higher. Since then, the number of U.S. deaths in alcohol-related crashes has declined from about 13,000 a year to about 10,000 a year. But the numbers haven’t changed much since 2010, so advocates have pushed states to take further measures to try to decrease the death toll.

Mothers Against Drunk Driving (MADD) champions laws that require all people convicted of drunk driving to install ignition interlock devices in their vehicles. The devices prevent the cars or trucks from starting unless the driver breathes into the machine and proves the person is not under the influence of alcohol. So far 25 states have passed that type of law in the last decade.

But a small group of advocates, particularly in the Midwest, backs a different approach that tries to make repeat offenders stay completely sober -- even when they're not driving. South Dakota pioneered the so-called 24/7 Sobriety method, and it has spread to nearby states, including North Dakota and Montana. Drivers who go through the program must check in twice a day, usually at the sheriff’s office, or use a monitoring bracelet to prove they’re sober. If they drink, they go immediately to jail for a short time -- usually no more than two days.

Both sides see serious flaws in the other approach, and their disagreements have now emerged at the federal level as a small part of Congress’ efforts to write a transportation funding bill. One of the many differences in the bills passed by the U.S. House and Senate is the way they treat 24/7 Sobriety programs. The Senate version is more friendly to that approach, but the House bill would keep the status quo. Negotiators from both chambers are trying to work out a compromise before the current funding bill expires Nov. 20.

Federal law currently specifies that a percentage of highway safety money can go only to states that require first-time drunk driving offenders to install ignition interlocks. Advocates for 24/7 Sobriety, including the American Beverage Institute, want states using their method to qualify for that money too. MADD adamantly opposes the change.

“We don’t want states doing all-offender interlocks and think that a 24/7 program is equal to it. It’s not,” says J.T. Griffin, MADD’s chief government affairs officer. “24/7 is much more geared toward the third-time, multiple drunk driver. Ignition interlocks for all offenders is geared toward the big picture of dealing with drunk driving and really bringing down the numbers of deaths and injuries because of drunk driving.”

But backers of the sobriety checks say drunk drivers can easily avoid installing ignition interlocks or drive vehicles without them. The offenders often revert to drunk driving once the ignition interlocks are removed, said Anastasia Swearingen, the director of government affairs for the American Beverage Institute, which supports 24/7 Sobriety. “We need a policy option that is actually going to stop people from drinking and driving.”

A rural highway in South Dakota, which pioneered the 24/7 Sobriety approach. (FlickrCC/faungg)

New Mexico, which grappled for years with high rates of drunk driving, became the first state to require all motorists convicted of drunk driving to install ignition interlock devices on their vehicles back in 2005. MADD still touts it as a model for other states. The yearly number of deaths in alcohol-related crashes plummeted by 41 percent since the law took effect, compared to a 23 percent decline nationally.

New Mexico’s ignition interlock law, though, was part of an even bigger effort to crack down on drunk driving that started in 2005. Then-Gov. Bill Richardson appeared in anti-drunk-driving commercials and even appointed a drunk driving czar to his cabinet. The federal government also paid five counties to increase their police enforcement of drunk driving laws.

With so many different policies, it’s hard to give credit to just one of them. While other states with all-offender interlock laws -- Alaska, Arkansas, Hawaii, Kansas and Utah -- also saw significant decreases in alcohol-related vehicle deaths after enacting their laws, critics point out that the effects of ignition interlocks have not been examined using rigorous peer-reviewed studies that compare the behavior of drivers who use ignition interlocks against a control group.

Colonel Tom Butler, the head of the Montana Highway Patrol, who supports 24/7 Sobriety, said for years he tried using conventional methods -- including ignition interlocks – to combat drunk driving but still “led [the] nation in every bad statistic related to DUI.” When drunk drivers killed two Montana highway patrol officers in 2008, though, the agency started looking for new approaches.

For Butler, and other backers of the 24/7 Sobriety approach, ignition interlocks pose many problems.

The first is that only about 15 percent to 20 percent of offenders who are ordered to install the interlocks actually do, according to the National Highway Traffic Safety Administration. States don't have the resources to check to make sure drivers install them, and drivers often must pay a monthly fee to maintain the interlocks. Many drivers don’t bother.

Another concern with interlocks, the 24/7 Sobriety advocates say, is that offenders who install the devices are less likely to get arrested for another drunk driving offense only as long as their interlock is on. Once it’s gone, they’re just as likely to get arrested for drunk driving again as drivers who never had the device installed.

Then there are practical matters.

It’s no coincidence that 24/7 Sobriety is more popular in large, rural states. The distance to major towns makes it hard to install or maintain ignition interlocks or, for that matter, for a company to make money installing them. Interlocks are easy to avoid for many drivers, since many residents have several vehicles to choose from. Earlier models of interlocks had problems working in cold weather, a major factor on the northern Plains, which could mean even sober drivers could be stranded in harsh conditions.

Some critics have attacked 24/7 Sobriety for violating civil liberties, but the program won a major legal victory this year. In that case, a Montana driver challenged the constitutionality of the 24/7 Sobriety program, which he had to go through as a condition of his bail after being arrested for drunk driving. Robert Spady claimed the twice-daily sobriety checks were illegal searches that violated the Fourth Amendment. He also argued that it amounted to excessive bail, because participants are required to pay $2 per test.

But the Montana Supreme Court upheld the law this July. The court said the breath tests were not illegal searches, because the participants had already been taken into police custody, where privacy expectations are low. The court held the fees were not excessive bail, because they were not punitive and only paid the administrative costs of the program.

Like MADD, 24/7 Sobriety proponents believe data is on their side. The RAND Corporation has studied the approach. In one study, its researchers found that the constant check-ins reduced repeat drunk driving arrests by 12 percent and domestic violence arrests by 9 percent in South Dakota counties. But RAND researchers have also called for more research comparing the effectiveness of 24/7 Sobriety and ignition interlocks.

The reduction in recidivism under 24/7 Sobriety is a major selling point for Butler from the Montana Highway Patrol. As an alternative to jail, the program can save space in overcrowded facilities, but the effects can be even larger, he said.

“We are pulling people out of jail and allowing them to work and function as normal citizens,” Butler said. “That has a significant effect on taxpayers’ expense and also a significant effect on the families of people who may have previously ended up in jail. We want to make things better, and this will have a long-term impact on citizenry.”