Putting the brakes on nighttime driving by teen-agers is a road-safety idea whose time may have finally come - or at least is on the way. Proposals to restrict the use of motor vehicles by youths to daytime and early evening hours are expected to surface in several states in the next few years, if not months, according to those close to the scene. Such laws are in force in 12 states.
Lawmaker interest in some type of curfew legislation appears to have been spurred by the somewhat startling results of a study, involving crashes by 16 -year-old motorists, released last fall by the Insurance Institute for Highway Safety (IIHS).
The analysis comparing the nighttime road-accident records in four of the states with some kind of partial driving ban on youths, concludes that such measures ''substantially reduce'' the number of crashes.
In Pennsylvania, for example, the researchers project that the more than decade-old curfew law there contributed to 69 percent fewer vehicle accidents during curfew hours than otherwise might be the case, based on crashes by 16 -year-old drivers in neighboring Ohio, where there is no such restriction.
The study similarly estimates that such measures in New York has helped hold down night crashes by 62 percent. For Maryland and Louisiana, the other two curfew states studied, there were 40 and 25 percent fewer road accidents respectively during the driving restriction hours.
In Maryland, where the comparison involved the average crash rate involving 16-year-olds between 1974 and 1978 (when the law was enacted) and 1979 and 1980, the annual number of crashes dropped by 338.
While declining to speculate how passage of such laws in other states might boost highway safety, William Haddon Jr. MD, president of the IIHS, views these curfews as a significant ''way to put a dent in drunk driving and crashes by teen-agers.''
He and other boosters of strong laws warn that having one on the books is only a partial step. To be effective it must be followed by rigid enforcement.
Many of the present measures, most of which are more than a decade old, ''are very weak'' Dr. Haddon asserts. Even the toughest measures include exceptions. For example, young drivers are often permitted to drive during the curfew hours if on the way to or from work or school.
Curfew hours vary widely from state to state. It is 9 p.m. to 5 a.m. in New York, 11 p.m. to 5 a.m. in Louisiana, midnight to 5 a.m. in Pennsylvania; and 1 a.m. to 6 a.m. in Maryland.
Some foes say curfews would not be necessary if the minimum drinking age is raised and enforced, since the lion's share of youth-involved traffic accidents are liquor related. Others suggest that restricting the hours a teen-ager can drive is unfair to young people who are responsible when they get behind the wheel.
Backers of curfew legislation, however, cite National Safety Council statistics which show that teen-agers, who comprise 8 percent of the licensed drivers, account for 21 percent of the traffic accidents.
Besides Louisiana, Maryland, New York, and Pennsylvania, states with some sort of driving hour restrictions for youths include Illinois, Indiana, Massachusetts, Michigan, South Carolina, South Dakota, Wisconsin, and Wyoming.