Germany is an interesting case in point on this issue. They've been way ahead of the rest of the world with things like recycling for years but I just found out from a friend who lives there that the government now check the exhaust emissions of every vehicle every year or so. If the car is emitting too much carbon monoxide (meaning it lacks in efficiency) it has to be tuned or repaired or it is considered unroadworthy and can't be driven.
This not only improves pollution emissions but also fuel usage and sustainability. It also encourages manufacturers to build more fuel-efficient vehicles to meet tighter limits. One of the other benefits is that the more responsive a car is to acceleration (because it is well-tuned and not requiring repair to its fuel intake and exhaust systems) the less likely is it to be involved in an accident. A common cause of accidents is cars that don't respond quickly enough to not only braking but also acceleration, so this also reduces medical and insurance costs. No doubt the rest of the world will realise the benefits of this system one day.