It would have seemed a good idea at the time; put restrictions on the youngest drivers, the ones that proportionally die most in accidents. Prohibit them taking to the road during the more dangerous nighttime and limit the number of passengers these driving beginners can carry. The United States led the way with these graduated drivers license (GDL) programs and the idea continually bobs up in Australia.

And sure enough a recent study shows that stronger GDL programs are associated with lower incidence of fatal crashes for 16-year-old drivers, compared with programs having none of the key GDL elements. The findings are published in this week’s Journal of the American Medical Association (access to the free abstract available here with a story based on the journal article on the NPR website).

Yet the figures in the US show that fatal crash incidence among teen drivers increased with age, from 28.2 per 100 000 person-years (16-year-old drivers) to 36.9 per 100 000 (17-year-olds), before reaching a plateau of 46.2 per 100 000 (18-year-olds) and 44.0 per 100 000 (19-year-olds).

And the conclusion of the authors?

In the United States, stronger GDL programs with restrictions on nighttime driving as well as allowed passengers, relative to programs with none of the key GDL elements, were associated with substantially lower fatal crash incidence for 16-year-old drivers but somewhat higher fatal crash incidence for 18-year-old drivers. Future studies should seek to determine what accounts for the increase among 18-year-old drivers and whether refinements in GDL programs can reduce this association.

The Los Angeles Times is somewhat more forthright in its interpretation:

For more than a decade, California and other states have kept their newest teen drivers on a tight leash, restricting the hours when they can get behind the wheel and whom they can bring along as passengers. Public officials were confident that their get-tough policies were saving lives.

Now, though, a nationwide analysis of crash data suggests that the restrictions may have backfired: While the number of fatal crashes among 16- and 17-year-old drivers has fallen, deadly accidents among 18-to-19-year-olds have risen by an almost equal amount. In effect, experts say, the programs that dole out driving privileges in stages, however well-intentioned, have merely shifted the ranks of inexperienced drivers from younger to older teens.