TUCSON, ARIZ. ? As Illinois lawmakers consider a proposal that would make the state’s teen driver licensing system one of the nation’s most stringent, top researchers say such laws are saving young lives in states where they have been enacted, but much remains to be done.

Placing restrictions on teen licenses “is clearly the best policy intervention we have so far to reduce teen driving deaths,” said Daniel Keating, who studies adolescent development and the teen brain at the University of Michigan. “It has the biggest bang for the buck.”

Every state has some component of Graduated Driver Licensing, but the rules vary greatly, creating a patchwork of systems with varying restrictions. In states with the most limitations, researchers say, fatality rates have declined in recent years.

In Kansas, learner’s permits can be obtained at age 14; restricted licenses at 15; and regular licenses at 16.

“If you have a cancer cure, don’t you think everyone would want it?” Keating asked more than 100 experts who gathered here last week to share the latest research on the teen-driving problem, which bolsters the case for more stringent driver’s license laws.

Upgrades to graduated licensing laws often have been slowed by perceived opposition from parents who think they are too busy to conduct additional practice driving with their teens and want to be relieved from chauffeuring duties.

For that and other reasons, many states have failed to enact graduated licensing laws that have all of the provisions experts consider most effective in reducing deaths. Only about half scored “good” for graduated licensing laws in recent ratings by the Insurance Institute for Highway Safety.