Graduated driver's license laws — designed to ease young drivers toward full driving privileges — have saved lives and reduced crashes.
The laws, which began to appear in the United States two decades ago, gradually move teens through three licensing stages.
"The aim of these measures is to take teens out of the riskiest driving situations," says Russ Rader, spokesman for the Insurance Institute for Highway Safety (IIHS) and the Highway Loss Data Institute (HLDI).
States with the toughest GDL laws have 30 percent lower rates of fatal crashes among teens ages 15 to 17, compared to states with the weakest laws, according to data from the IIHS/HLDI.
Every state has some type of GDL program. But several states have room for improvement, according to a March 2015 IIHS/HLDI analysis. If those states were to toughen GDL laws, they could reduce the rate of fatal crashes by about 45 percent or more among drivers ages 15 to 17.
Here’s a look at the 10 states with room for improvement — and five steps the states could take to make teens safer.
South Dakota: Potential reduction in fatal crashes: 63 percent
South Dakota has more room to improve than any other state, according to IIHS/HLDI.
"South Dakota has a weak law, with the youngest driving age in the country," Rader says.
Teens can get an instruction permit to drive at age 14 and full license privileges by age 16.
South Dakota does not require new teen drivers to have an adult supervisor in the car when transporting other teens. IIHS/HLDI believes fatality rates would drop if South Dakota limited teen drivers to having just one other teen — or no teens at all — in the car when an adult is not present.
Key change No. 1: Raise the permit age. IIHS/HLDI studies have found that delaying the permit age by one year drops fatal crash rates by 13 percent among teens ages 15 to 17.
Kara Macek, spokeswoman for the Governors Highway Safety Association, says the teen brain is in a particularly vulnerable state of development.
"It just makes sense that the longer you wait to begin driving, the more mature you are," she says.
North Dakota: Potential reduction in fatal crashes: 56 percent
North Dakota could see a 56 percent reduction in teen fatal crashes with tougher GDL laws, IIHS/HLDI says. The state also places no restrictions on teen drivers who wish to transport another teen.
Key change No. 3: Raise the license age. Not only does IIHS/HLDI recommend that states increase their permit age, but it also would like to see states push actual licensing later into a person's teen years.
As with raising the permit age, increasing licensing age by one year drops fatal crash rates among teens 15 to 17 by 13 percent, according to IIHS/HLDI.
Iowa: Potential reduction in fatal crashes: 55 percent
Tougher GDL laws in The Hawkeye State could result in a 55 percent reduction in teen fatal crashes, IIHS/HLDI says.
Like the Dakotas, Iowa allows new teen drivers to transport other teens without an adult passenger present.
Key change No. 2: Increase practice hours. A study by the HDLI found that increasing required practice hours by 40 hours reduces insurance collision claims by 10 percent among drivers who are 16 or 17.
All teens who get learner's permits should have at least 50 hours of parent-supervised driving practice, says Kathy Bernstein, senior manager of teen driving initiatives at the National Safety Council.
Montana: Potential reduction in fatal crashes: 53 percent
In Montana, tougher GDL laws could reduce teen fatal crash rates by 53 percent, IIHS/HLDI says.
IIHS/HLDI notes that Montana allows teens to obtain a learner’s permit at age 14.5 and a license at age 15. Boosting the learner’s permit age to 15.5 and the licensing age to 16 could reduce fatal crashes by 26 percent among drivers ages 15 to 17, IIHS/HLDI says.
Key change No. 4: Restrict nighttime driving. Nighttime presents a unique set of challenges for all drivers, regardless of age or experience, Bernstein says.
"It is more difficult to spot hazards, and there tend to be more impaired drivers on the roads," she says.
Bernstein notes that teens do not need to be driving late at night to be at risk. Most fatal teen nighttime crashes occur before midnight, she says.
Arkansas: Potential reduction in fatal crashes: 50 percent
Arkansas could see a 50 percent reduction in teen fatal crashes with stricter GDL laws, IIHS/HLDI says.
Arkansas is one of eight states that do not require new teen drivers to get a minimum number of supervised practice sessions before obtaining an intermediate license, IIHS/HLDI says.
Key change No. 5: Limit the number and type of passengers allowed. Bernstein says one recent study found that just one young passenger increases a teen driver's fatal crash risk by 44 percent.
"Teen drivers are not experienced enough to handle distractions in the vehicle, and passengers can be the most significant distraction," she says.
The rest of the states that could benefit from strong GDL laws
Idaho: Potential reduction in fatal crashes: 49 percent
Mississippi: Potential reduction in fatal crashes: 48 percent
New Mexico: Potential reduction in fatal crashes: 47 percent
Kansas: Potential reduction in fatal crashes: 46 percent
South Carolina: Potential reduction in fatal crashes: 45 percent
While much progress has been made in the past two decades, Rader says the rate of improvement in GDL laws has slowed in recent years.
He adds that the reasons for the slowdown are unclear, and he also notes that the slowdown coincided with an uptick in the number of states enacting measures to restrict cellphone use and texting.
"There's only so much bandwidth in state Legislatures for dealing with traffic safety problems along with all the other things they have to do," he says.
Even so, IIHS/HLDI urges lawmakers in all states to ask themselves if they have done everything they can to keep young drivers safer.
"In most cases, the answer is 'no,'" Rader says. "Every state has room for improvement."