It's probably not a good idea to buy a car for a teenager, but for parents inclined to do so, financial prudence is recommended: They will not drive with the same skill as an older person, the risk of accident is higher, they may not know how to maintain it and those things all add up to expensive mistakes.

But a new study finds that almost 50% of teen drivers killed on US roads in the past few years were driving vehicles that were 11 or more years old. So is that because more teens are driving older cars because they are more accident prone, or that cars in the 1990s and early 2000s somehow lacked safety features a newer car might? 

A new paper in Injury Prevention claims the latter, that cars were more dangerous then. and that parents could be putting their children's lives at risk by focusing on cost.

That needs some context. Fatal road traffic collisions among US teens have actually fallen sharply since 1996, though teens remain terrible drivers. Per mile driven, rates of police-reported and fatal crashes involving teens are around three times those for adult drivers.

The researchers analyzed data from the US Fatality Analysis Reporting System for 2008-12. FARS collects information on all vehicle collisions on US public roads that result in at least one death within 30 days of the incident. Using vehicle information databases, they compared the types, sizes, and ages of vehicles driven by 2420 teen drivers (15-17 year olds) with those driven by 18,975 middle aged drivers (35-50 year olds).

Two thirds of the teen drivers who died were in a car: 29% were driving a mini or small car; and just over one in three (35%) were driving a mid-size or larger car. The rest were driving pickups (17%) and sport utility vehicles, otherwise known as SUVs (17%).

Fatally injured teen drivers were significantly more likely than middle aged drivers to have been at the wheel of a small or mini car (29% vs 20%) or a mid-size car (23% vs 16%), and significantly less likely to have been driving a large pickup (10% vs 16%).

So parents who know teens are more likely to have an accident were making sure it happened in older cars. Most of the teen drivers (82%) who were killed, were in vehicles that were at least 6 years old. A third (34%) were 6-10 years old, and a similar proportion (31%) were 11-15 years old. Some 17% of the vehicles involved in fatal collisions were 16 or more years old. 

The authors believe Electronic Stability Control (ESC) would have made a big difference, though there is no way to know that. Fatally injured teens were almost twice as likely as middle aged drivers to be driving a car that was 11-15 years old (20% vs 12%). Only around one in 10 of the fatally injured teens' vehicles had ESC available as standard (3%) or as an optional feature (8%). ESC is useful in cases where the driver loses control - something that is relatively common among young drivers who have just passed their driving test, say the researchers. It can cut the risk of death in single vehicle crashes by around half and by 20% in crashes involving several vehicles.

In all, only around a third (36%) of teen and middle-aged drivers' vehicles had optional or standard air bags, but the vehicles driven by adults were slightly more likely to have them as standard equipment.

Given that teen drivers are more likely to be involved in road traffic collisions than older drivers, it is especially important that they drive vehicles fitted with key safety features, which afford good protection in the event of a crash, say the authors.

"Larger, heavier vehicles generally provide much better crash protection than smaller, lighter ones," they write, pointing out that even when teens were driving cars, 2 or fewer years old, these tended to be small or mini.

"Newer vehicles generally are also more likely to have better crash test ratings and important safety features such as ESC and side airbags," they say, adding: "Parents may benefit from consumer information about vehicle choices that are both safe and economical."