Devices that require convicted drunken drivers to pass a breath test before starting their cars save lives and could save even more, according to a Johns Hopkins study published Thursday.
The study found a bigger drop in drunken driving-related fatalities in states that required so-called ignition interlocks for anyone convicted of driving under the influence than in states that limited their use to repeat offenders.
States increasingly have adopted laws requiring the devices in an effort to reduce fatal road crashes. Last year, Maryland became one of 28 states that have made the interlocks mandatory for everyone convicted of driving under the influence, after the bill was stymied for years by lawmakers who thought the requirement was burdensome on first-time offenders.
"These interlock laws are increasingly common, but they can still be controversial because they impose a pretty big imposition on people who have to install them," said Emma E. "Beth" McGinty, deputy director of the Johns Hopkins Center for Mental Health and Addiction Policy Research at the Bloomberg School of Public Health. "And until recently, we haven't had good data on how they affected fatal crashes, which was the goal of the laws."
The Maryland law passed largely because of lobbying by advocates armed with tragic crash stories, including the death of Montgomery County Police officer Noah Leotta, who was fatally struck by a drunken driver. His family took up the push for what became known as "Noah's Law."
With about a third of automobile crash deaths nationwide resulting from impaired driving, a statistic that hasn't budged much in recent years despite fewer overall crashes, Johns Hopkins researchers and advocates for stronger drunken-driving measures say the study findings should bolster efforts to expand use of the technology.
The study published in the American Journal of Preventive Medicine found at least a 7 percent drop in fatalities when interlocks were mandatory for everyone convicted of driving with blood-alcohol concentration over the legal limit, compared with about a 2 percent drop when the devices were limited to repeat offenders or those with high alcohol levels.
That translated into 1,250 fewer alcohol-involved crash fatalities in states with more expansive laws.
The researchers looked at three decades of crash data and compared states with limited and expanded laws, and data from within states that expanded their laws. They also considered other factors that reduce road deaths.
Advocates such as Mothers Against Drunk Driving say expanded interlock laws may be more effective than license suspensions because other research has found that up to 75 percent of people with suspended licenses drive anyway.
Interlock technology has been around since the 1980s, and states such as Oklahoma and Oregon became early adopters, McGinty said. The technology has become more accurate and easier to install over time, but national data had been limited on their effectiveness. She believes there were no quality studies comparing limited and expanded use of interlocks before the Hopkins study.
Some national groups continue to oppose interlocks for all offenders, including the American Beverage Institute, which said interlocks are expensive and burdensome to install and monitor. Instead, beverage industry officials said in a statement, the focus should be on "policies targeting hard-core drunken drivers, including ignition interlocks for high-[blood alcohol concentration] and repeat offenders, roving police patrols, and encouraging smart, responsible alcohol consumption."
The Maryland law applies to any driver arrested with a blood-alcohol concentration of 0.08 or higher and requires interlocks for six months for first-time offenders to two or three years for repeat offenders. License suspension periods also were extended under the law.
McGinty said bills in some states may lose steam as public attention focuses on the nation's opioid epidemic and away from alcohol. More people now die of overdoses from opioids such as heroin and prescription painkillers than in alcohol-related car crashes. About 10,000 people die annually in drunken-driving-related accidents, and the number has been dropping for a number of reasons including enforcement. More than three times that number die of opioid overdoses and the number has been rising.
Advocates from MADD say drunken driving remains a major U.S. killer needing attention. They reject that the interlock laws are burdensome, with most of the $1,000 or so a year for installation and monitoring paid for by users or fees paid by the interlock companies. State laws including Maryland's aim to be budget neutral.
Frank Harris, director of state government affairs for MADD, said interlocks allow drivers to retain their freedom to drive wherever they like, provided they are sober.
The interlocks are now an integral part of enforcement and growing — a trend Harris said could accelerate now that Hopkins has added to the evidence that they work.
"A 7 percent change is significant," he said of the reduction in crash fatalities.
Officials at the Maryland Motor Vehicle Administration say it's too soon to provide data on how the state's expanded interlock law is making a difference because it only went into effect in October. Chuck Brown, an MVA spokesman, said that in 2015, the state's more limited interlock law prevented 4,000 trips by drivers with blood-alcohol concentrations greater than the legal limit.
The Maryland State Police reported that they made 1,656 impaired-driving arrests from October to January, compared with 1,742 during the same time period the year before, but other factors could be causing the decline, said Greg Shipley, a police spokesman.
"We certainly hope the ignition interlock requirement will be a deterrent and hope Maryland will experience the same decrease as reflected in the Hopkins survey," he said.
This story has been updated to reflect that Noah Leotta was a Montgomery County Police officer.