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Status Report, Vol. 44, No. 7 | July 11, 2009 Subscribe

Interlock laws now cover more DUI offenders

Six states have upped the ante for any driver who drinks too much alcohol and then gets behind the wheel. Arkansas, Hawaii, Utah, and Wyoming strengthened ignition interlock laws to include first-time driving under the influence (DUI) of alcohol offenders. New Mexico toughened requirements for first-time offenders, and Minnesota expanded a two-county interlock pilot program aimed at repeat offenders, creating a statewide program that also includes first timers. Interlock laws targeting first offenders may yield stronger results in preventing alcohol-impaired driving since about two-thirds of drivers arrested in the United States each year are first offenders.

Alcohol ignition interlocks prevent drinking drivers from starting their vehicles. These devices have a breath-testing unit that is connected to the vehicle ignition. To start the vehicle, the driver must blow into the device and register a blood alcohol reading below a predetermined level. If the reading exceeds it, the engine won't start.

Arkansas, Hawaii, and Utah join nine states (Alaska, Arizona, Colorado, Illinois, Louisiana, Nebraska, New Mexico, Oregon, and Washington) in requiring all DUI offenders, including first timers, to put ignition interlocks in their vehicles as either a condition of relicensing during suspension or as a requirement for reinstating their license. Arkansas's new legislation includes a 6-month license suspension for a first offense and allows an immediate ignition interlock restricted license.

In Utah, DUI offenders now will receive a license suspension for at least 120 days, up from 90 days, and become interlock-restricted drivers for 18 months after conviction. Hawaii similarly extended its license revocation period for drivers convicted of DUI from 3 months to a year. During this revocation period, offenders may only drive vehicles equipped with interlocks.

Wyoming joins the ranks of states that require first-time offenders to use an ignition interlock by adding a 6-month requirement for first timers with a blood alcohol concentration (BAC) at or above 0.15 percent. New Mexico tightened its legislation by stipulating that convicted alcohol-impaired drivers have an interlock on their vehicle for 6 months before full driving privileges can be reinstated. This may help close any gaps where drivers wait out a suspension period without ever getting an interlock. 

 "Strengthening interlock laws to include first-time offenders is a logical step in curbing alcohol-impaired driving since ignition interlocks have been shown to reduce repeat offenses," says Anne McCartt, Institute senior vice president for research. "The broader use of interlocks should help restart progress in reducing alcohol-impaired traffic crashes."

A 1999 Institute study of repeat offenders showed interlock restrictions reduce the risk of committing an alcohol-related traffic violation within the first year following conviction by nearly 65 percent (see "Ignition interlocks reduce re-arrest rates of alcohol offenders," Jan. 15, 2000).

Scope of problem

In 1982 about half of all drivers killed in crashes had BACs of 0.08 percent or more. By 1997 this proportion had declined to 32 percent. But the progress hasn't continued. Since 1997 there has been virtually no change in the proportion of drivers who were killed in crashes with BACs of 0.08 percent or more (see "No recent progress: Impaired-driving deaths aren't declining anymore," Feb. 8, 2003).

All 50 states and the District of Columbia have per se laws making it a crime to drive with a BAC at or above 0.08 percent. Most states (47 and the District of Columbia) allow or require ignition interlocks for at least some repeat offenders, and some laws also apply to first offenders with very high BACs, usually at or above 0.15 percent.

Alcohol-impaired driving remains a big factor in crash fatalities today, and most impaired drivers are never caught. An estimated 90 million vehicle trips per year involve alcohol-impaired drivers, but only 1.5 million of these end in an arrest (see "Focusing too much on hardcore drinking drivers is counterproductive," Sept. 7, 2006).

During 2007, 12,998 people in the U.S. died in crashes involving a driver with a BAC at or above 0.08 percent, representing 32 percent of all traffic-related deaths. Institute research indicates almost 9,000 of these deaths would have been prevented if all drivers' BACs had been less than 0.08 percent.

New detection technologies

A partnership between the National Highway Traffic Safety Administration and the Automotive Coalition for Traffic Safety, a consortium of automakers, is exploring the potential for advanced in-vehicle technology to prevent alcohol-impaired driving among all drivers with BACs at or above the legal limit, not just those who have been convicted of DUI.

The Driver Alcohol Detection System for Safety (DADSS) program is a 5-year initiative to research, develop, and test technologies that detect alcohol in a driver's system quickly, accurately, and unobtrusively. Potential technologies range from analysis of air samples in the vehicle passenger compartment, to tissue spectroscopy which can estimate BAC by assessing light absorption at a particular wavelength based on measurements of light reflected from the skin, and systems that assess alcohol emission through the skin by touch.

Now in its second year of work, DADSS has contracted with three companies to develop technologies. TruTouch, a New Mexico firm specializing in alcohol detection technology, will develop a prototype using the tissue spectroscopy method. Alcohol Countermeasure System, an alcohol ignition interlock and breath tester manufacturer based in Canada, and Autoliv, a Swedish automotive safety systems maker, will work on breath technologies. During the next 12 months 3 prototypes are expected to emerge from these efforts.

"We look forward to conducting laboratory and human subject tests of these new technologies," says Susan Ferguson, program manager for DADSS. "We'll know how close they've come to meeting our requirements, and how much there is left to be done." The Institute participates on an expert panel advising the initiative.

All drivers
Lives that would be saved by reducing BACs to
Less than 0.08% 8,893
Less than 0.05% 11,141
Zero BAC 13,600
Drivers 1+ prior DUI
Lives that would be saved by reducing BACs to
Less than 0.08% 691
Less than 0.05% 838
Zero BAC 984

Note: zero BAC defined as less than 0.02%

To better understand the potential benefits of alcohol interlock devices, the Institute looked at the estimated number of fatal crashes involving drivers at various blood alcohol concentrations (BACs) in 2007, as reported by the National Highway Traffic Safety Administration in the Fatality Analysis Reporting System. Combining this information with the increased fatal crash risk that's associated with different BACs, Institute researchers estimated the potential lives saved if ignition interlocks were used to prevent drivers with specified BACs from getting on the road. They also calculated an estimate for all drivers with a driving under the influence conviction in the past 3 years.

During 2007, 15,104 deaths occurred in crashes in which at least 1 driver had a positive BAC (0.02 percent or greater). There were 12,998 fatalities among those drivers with a BAC at or above 0.08 percent. If no drivers had had BACs at or above 0.08 percent, an estimated 8,893 deaths would have been prevented. These estimates update previous work (see "Reducing BACs to the legal limit could save almost 9,000 lives per year," Oct. 13, 2007).

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