Proposal for the US: shift teens from cars to smaller vehicles: mopeds, scooters, and very small displacement motorcycles - 50, 100, 150 cc engines - and tie advancement in license class/engine size to both age and other achievements: graduating high school or getting a GED, completing an associate degree or technical program, graduating college, completing military or national service, or being employed for X hours per week.

Put strong negative incentives in place for motor vehicle violations - temporary downgrade in license class, bump in insurance costs, delay in advancement to next license class.

This would significantly increase the number of small vehicles on roads while decreasing the power and weight of vehicles being operated by less experienced drivers. It would provide a easily visible way for young people to display their level of age and accomplishment (or lack of it).

Operators of larger vehicles would have to deal with the presence of many more smaller vehicles, which could have a herd immunity effect - with 10x scooters on the street, car drivers would be more likely to notice and avoid two-wheelers of all sizes. Reduced carbon output would be another benefit.