Graduated licensing laws the Institute rates good are associated with lower fatal crash rates among teen drivers and lower insurance losses, compared with laws rated poor. Strong restrictions on nighttime driving and teen passengers, as well as delayed licensing age, also reduce fatal crashes and insurance losses. These are the main findings of a pair of studies by the Institute and affiliated Highway Loss Data Institute.
"First we looked at teens' fatal crash rates based on the overall strength of the graduated systems in each state," explains Anne McCartt, Institute senior vice president for research. "Then we looked at the specific elements of each system to tease out their effects. Doing the same for insurance claims data gave us more insight into all kinds of crashes, not just the most severe ones. We found that strong laws affect everything from minor fender benders to fatal impacts."
Teens are overinvolved in crashes. The fatal crash rate per mile among 16-19 year-olds is 4 times as high as for older drivers. To address this toll (4,342 deaths of people of all ages in crashes involving teen drivers in 2007), states have adopted graduated systems that phase in driving by young beginners as they mature and develop skills. States with these systems reduce crashes 10-30 percent.
Since 2000, the Institute has rated states' young driver licensing laws. Key components include a learner's stage beginning no earlier than age 16, lasting at least 6 months, and requiring a minimum of 30 practice hours, as well as an intermediate stage that permits no more than 1 teen passenger and prohibits driving after 9 or 10 p.m. These restrictions should last a year or preferably until age 18.
Based on the Institute's current rating system, no states in 1996 had laws rated good, but there has been progress. Now the laws in 31 states and the District of Columbia are rated good, 12 are fair, 7 are marginal, and no states are poor.
Using data on 1996-2007 fatal crashes, researchers looked at how the laws affect teen drivers' per-population fatal crash rates. The upshot is that the Institute's rating system lines up well with reductions in the rates among 15-17 year-olds. The better the overall rating, the bigger the fatal crash rate reduction. Graduated systems rated good had 30 percent lower rates than systems rated poor. Fatal crash rates were 11 percent lower where the laws are rated fair.
The Highway Loss Data Institute's analysis examined claims data for rated 16-17-year-old drivers per insured vehicle year (an insured year is 1 vehicle insured for 1 year or 2 insured for 6 months each, etc.). For insurance purposes, a rated driver typically is considered to represent the greatest loss potential for an insured vehicle.
For laws rated good, researchers determined that the frequency of claims under collision coverage was 16 percent lower among drivers 16 and 17. Losses were 13 percent lower in states with laws rated fair and 10 percent lower where the laws are marginal. Relatively minor crashes dominate collision claims. About half are for damages less than $2,000. Losses in this study were examined for vehicles 3 years old or newer in 1996-2006.
Both studies confirm that the licensing age is an important factor. The older this age, the fewer fatal crashes there are per population. A 6-month delay, from 16 to 16½ for example, lowered 15-17 year-olds' fatal crash rate by 7 percent. A 1-year delay lowered it by 13 percent. Likewise, delaying the licensing age by 1 year reduced the collision claim frequency by 12 percent among 16 year-olds.
"An older licensing age means fewer teen drivers and lower exposure, so it's not surprising that delaying this age makes a difference in crashes per population," McCartt explains. "The effect for insurance losses, though, applies only to licensed drivers, so an older licensing age means that when teens do get their licenses they're safer drivers."
Most U.S. states license at 16, 16½, or somewhere in between, and a few license younger than 16. Only New Jersey waits until 17, which lowers fatal and injury crash rates per population (see "Licensing teenagers later reduces their crashes," Sept. 9, 2008).
Passenger and nighttime restrictions significantly reduce fatal crash rates and insurance losses. For example, the fatal crash rate of 15-17 year-olds was 21 percent lower when the beginners were prohibited from having any teenage passengers in their cars versus allowing 2 or more. Allowing only 1 passenger reduced the rate by 7 percent. Driving restrictions beginning at 9 p.m. cut fatal crashes an estimated 18 percent versus no restrictions. The reduction was 12 percent where 15-17 year-olds' driving was limited after midnight.
For insurance losses among 16-17-year-old drivers, restricting the number of passengers to no more than 1 resulted in a 6 percent decrease. Imposing a 9 p.m. nighttime driving restriction resulted in an 11 percent reduction in collision claim frequencies.
Graduated licensing usually includes a minimum period for a learner's permit. Increasing how long a learner has to stay in this stage delays the age for an intermediate license and gives teens more supervised practice opportunities. The results show the benefits of delayed licensure, but neither study found an additional benefit for permit holding.
Another aspect of graduated licensing involves the amount of practice behind the wheel that learners are required to get, and findings are mixed. A 20-hour increase in required practice reduced the risk of collision claims by 4 percent among teens once they got licenses. However, practice didn't affect the rate of fatal crashes per population.
"These studies show that graduated systems protect teens not only by delaying licensure but also by producing drivers who are less likely to crash," McCartt says. "States have made tremendous progress over the past 12 years, but it's clear that all graduated programs don't provide equal benefits. Many states still need to set strict limits for teens on night driving and teen passengers. It's also time for serious conversations about raising the licensing age for teens."