1. Depends on alternative transportation availability and expense. It may increase air pollution in some areas by increasing how many parents drive their more expensive, but less fuel efficient cars(like trucks and suvs) around town.

2. What does maturity and reliability have to do with recognizing a car is a metal box of death? 16 year olds have a well defined concept of danger, Most of them exhibit the same behaviors as most people new to driving would such as slowing down over a long distance, driving too close to the side of the road, turning too wide, jerky acceleration, etc. Once these new behaviors are overcame, they next need to learn defensive driving skills and learn how to anticipate other cars movements(something they are not alone with, seems most people, regardless of age needs to learn more of that). Also, they haven't experience though friends and family or though their own experiences the unlikely events which would scare them into driving the speed limit when its safe to go over, not tailing too closely, etc( actually, a lot of people never experience those things, like really serious car wrecks although they are likely to experience minor ones).

3. Simply reducing the number of drivers may not reduce the number of car accidents, in that distractions from passengers would increase, since car pooling likely would as well. Also the possible increase in car pooling would mean more lives are at risk per a crash.

I would also like to add:

4. Many 16-18 year olds work part time jobs, limiting their ability to travel to and from them isn't going to help the economy.

5. Many are also in other activities outside of school, these may keep them out of trouble. Limiting their ability to travel to and from them may increase crime, lower graduation rates, etc. For example, if a poor student really likes a Extracurricular activity in school, he may put extra time in his studies to meet the min academic requirements to participate in it. Also, these activities are structured, supervised and may channel a teen's energies into constructive purposes or at least non-destructive ones. Alternatives may very easily lack those qualities.

6. Raising the age limit pushes back learning how to drive to a more vital time in development, to roughly the time students enter college. A commuter college can be terrible with parking and traffic congestion, it would be bad to have most freshmen new to driving and trying to navigate the often confusing and infuriating road conditions of some college campuses. Similar things can be said of those who work in more congested areas, like in the downtown area of a city.

7. Raising the age limit creates a different set of circumstances insurance companies may not have experience with(creating a sense of greater risk, and thus a higher premium), it also creates greater demand for insurance during a period. Some teens do not learn how to drive till they have to(for most, roughly 18), while others learn as soon as possible. Making them all learn how to drive roughly when they have to will boast demand for insurance up, Possibly raising insurance companies volume per a period and thus costs(till they grow to handle the greater spikes in demand) These costs will be passed on to the consumer. A similar argument can be made with gasoline, except gasoline is more limited in supply and so just the increase in demand will cause price increases. Most people are born in august, so every year during august you'll price increase (unless a equal or greater number of people stop using such services, which is unlikely)

8. Many jobs require a valid driver's license and some experience with driving in order to operate some machinery, like a tug or forklift or preform some service like pizza delivery. Once people turn 18, they wouldn't be eligible for such jobs for at least a few months, and likely years.