The study, published in March in the Journal of Policy Analysis and Management, found that state GDL laws with nighttime driving curfews resulted in fewer arrests for certain crimes, such as larceny and assault, among 16- and 17-year-olds. It’s thought to be the first published study linking implementation of GDL with decreased criminal behavior.
All 50 states and the District of Columbia maintain different GDL laws that phase in driving privileges. All teens and older adults in some states must first complete a learner stage and an intermediate stage before obtaining licenses. Individual laws vary greatly from state to state. For example, teens are eligible for intermediate stage permits when they turn 15 in Idaho and Montana, but not until 17 in New Jersey. Also depending on the state, curfew hours prohibiting teens from driving while unsupervised start anywhere from 8 p.m. to 1 a.m.
When states first introduced GDL requirements, effects on criminal behavior weren't considered. The laws were largely designed to improve teen driver safety. But the study's authors contend that it’s an unintended consequence -- and a positive one -- that policymakers should take into consideration.
“There’s debate going on around this policy, and it is a really important social benefit that needs to be included,” said Daniel Litwok, a co-author of the study and senior analyst with the research firm Abt Associates.
In recent years, states have typically moved to strengthen existing GDL laws. Ohio, for instance, raised the age that drivers are subject to curfew hours and limits on passengers in vehicles last year.
The study, which focused on implementation of the intermediate phase of GDL, found that the introduction of GDL requirements decreased total arrests among 16- and 17-year-olds between 4.1 and 6.2 percent, depending on the control group used.
The single most important factor in reducing arrests was nighttime driving restrictions. As one would expect, states where teens must wait longer to obtain unrestricted driving privileges experienced much sharper declines in arrests than other states. Where driving curfews aren’t lifted until a person turns either 17 or 18, arrests dropped up to 8.1 percent for 16-year-olds and up to 9 percent for 17-year-olds.
Some crimes saw more notable changes than others. The study examined nine of the more serious types of crimes tracked in the FBI’s Uniform Crime Reporting program. Larceny arrests dropped between 5.3 and 6.7 percent, while aggravated assaults declined between 4.1 and 6.1 percent. GDL restrictions further led to declines in murders, although Litwok cautioned that it’s hard to gauge the effects of the laws with so few teenagers arrested for murder. GDL laws didn’t affect arson, burglary, motor vehicle theft, rape, robbery or other assault arrests.
Most GDL laws also limit how many passengers are permitted to ride with teenagers holding intermediate stage permits. But these rules had virtually no effect on criminal behavior, according to the study.
Researchers compared numbers of arrests for 16- to 17-year-olds with different sets of older control age groups ranging from age 18 to 24. Comparisons were made within each state within a particular age group for each year between 1995 and 2011 for 40 states without driving curfews prior to implementation of GDL laws. The study also independently controlled for the introduction of zero tolerance laws and truth-in-sentencing policies that require convicted offenders to serve large portions of their sentences.
For the most part, the fewer arrests simply resulted from taking teen drivers off the roads at night.
Traffic enforcement further plays a role in limiting teen driving. Most states allow for primary enforcement of nighttime driving restrictions, while 10 others consider it a secondary infraction, according to the Insurance Institute for Highway Safety. It’s difficult to say how often teens are cited, though, as data is mostly unavailable. New Jersey is unique in that it requires all drivers under 21 holding a permit or probationary license to display red decals on license plates. Some states also have exemptions allowing teens to drive at night for work or school.
The new findings follow years of research already indicating that GDL laws reduce teenage traffic fatalities. A 2010 analysis of state GDL laws found that the longer teens had to wait to obtain permits or licenses, the lower a state’s fatality rates were for 15- to 17-year-olds. Stricter nighttime restrictions similarly yielded lower traffic fatality rates.
