Compared to trucks, you basically use the roads for free on their dime.
Again, just because heavy trucks pay extra taxes doesn't mean that they cover their impact on the road system.
"Passenger vehicles account for 93 percent of all vehicle miles traveled on public roads in the United States. While large trucks account for just 7 percent of the miles traveled, they account for the most damage to the infrastructure."
"In the 1997 HCAS combination trucks were found, on average, to pay 90 percent of their Federal highway cost responsibility through user fees, but with changes in the fuel tax they now pay only 80 percent of their cost responsibility. The heaviest combinations, those over 80,000 pounds, pay only half of their cost responsibility."
So most trucks you see on the road pay 80-90% of their way already from a purely federal fuel-tax dollar standpoint. The gas tax is just the beginning for trucks. Now consider state licensing fees, permits, mandatory inspections, tolls that increase exponentially per axle, and what must be the ridiculous cost of compliance. Between the DMV and the DOT the papers that need filing fill a 3-ring every year, and there's a fee every other page. (I suppose the question of whether or not that money makes it back into road maintenance is bound to come up but that seems like a whole different issue.)
Seriously, put a sheep in the back of a pickup in Fresno and try to drive him to Seattle without doing anything illegal.
Loads are limited by weight per axle as to minimize the damage on the roads...not to mention that on a per pound of useful goods basis they are far more efficient than driving your 4000lb car to just haul your 100-300lb ass.
Where I live the majority of road damage is due to studded tires or weather...next time you are on a rutted highway notice how its not rutted for the dual tires that trucks have but it fits a normal car perfectly.
Beyond that, have you ever bothered to notice those little areas on the side of highways called weigh stations? You know, the ones where you don't have to stop? Yeah.
If anything, the subsidy runs from truckers to casual drivers, not the other way around.
The point is that heavy trucks don't pay enough taxes to cover their actual impact on the road-system.
The reason it doesn't happen is because then you've got to pay additional drivers, which outweighs the cost savings from avoiding the additional road use taxes.
I feel the need to add the qualifier that this is true of federal roads, but less so as we talk about local roads. I realize the story pertains to the interstate system, but as a cyclist the widespread misconception that gas tax funds all roads and other users are somehow freeloaders is quite detrimental.