Well if the government sets out to mandate something, it has the power to punish those who don't comply. So when the edict comes down to improve fuel efficiency

Well if the government sets out to mandate something, it has the power to punish those who don't comply. So when the edict comes down to improve fuel efficiency, auto-makers comply. Other dimensions not mentioned in the article: safety and affordability. A quick search shows that the affordability of cars has declined steadily, which makes it harder for the bottom of the economic ladder to get into a car. No car means it is harder to get to a job and climb up the ladder. It looks like road fatalities have declined over time, but I couldn't find data on non-fatal injuries. Also very interesting to see a whole lot of "they" and not a lot of "we" when defining what libertarians believe.