Actual cash subsidies for roads are minimal relative to the economic benefit.<p>This is another way to say that you could eliminate all subsidies on road construction&#x2F;maintenance, make everyone pay a sufficient per-mile tax, and the system would continue successfully more-or-less as it exists today<p>The same is not true of most public transit systems.<p>Now you can start arguing about implicit and explicit subsidies for suburbanization over the decades, but in the here-and-now, public transit is directly subsidized in a way that roads are not.