The first step in government control should be information dissemination and availability. To control vehicle speeds, first have "flowmeter"-type gauges, which would show momentary gas consumption, on all new cars and easily available for older cars. Maybe make them adjustable to gas prices to show dollar consumption.
Then I would support Jimmy Carter's plan (which was mostly a good token offer.) to increase gas tax five cents per gallon per year for several years. The main argument against this is that it would put an unfair burden on the poor, some of whom "need" their cars to drive to work, while not significantly hurting the rich. But the poor could save money by using mass transit, driving slower, driving smaller cars, motorcycles, bicycles or walking, and in many cases would be better off for it. Encouraging them to keep their fifteen year old Cadillacs is a way of giving them a false sense of dignity and status to keep them docile. Class injustice is a problem throughout society and should be dealt with as such, rather than on each issue.
Last (partly because it brings to mind images of Big Brother) we could have computerized spot checks, that would be able to identify individual cars, at random, changing locations along the highways. Then individual insurance rates would be calculated on the basis of average recorded speed, maximum speed, and speed relative to surrounding cars. As this system is expanded to check all cars on all major highways, it would greatly reduce car thefts, but also privacy. This is the kind of legislation which controls statistical numbers of people, while leaving the final decisions up to the individual.