Touche. I suppose I should have said "The vast majority of" instead of 90% of.
The fact remains that heavy vehicles (and I don't consider an SUV to be a heavy vehicle) inflict "the vast majority of" damage to our roadways. Cyclic loadings of automobiles over a long span of time will cause rutting; however, semi's will cause worse damage in a much shorter time period, and they are not paying the amount of taxes necessary to account for the amount of damage they are doing.
What is the ratio of automobiles to semi's in this country? I'd bet that it is at least 1000 to one. Who then is paying the lion's share of fuel taxes? And no, I don't have the data to back up these statements, other than the fact that 2 plus 2 equals 4. The fact that semi's do the vast amount of damage to roads is something that is self-evident and well-recognized by a second year transportation engineering student. Arguing otherwise is like saying that 2 plus 2 equals 3.
The correct solution is to build roads capable of handling the loads. I think that most roads are designed as such, but all of the finished roads that I see are later sampled and found to be built in a substandard manner. There are thousands of DOT vs Contractor lawsuits all over America over just such problems. I know of at least two major projects here in central FL (Interstates) where contractors are being sued by DOT after completion of the project with areas of these roads requiring significant remediation efforts within weeks of them opening the road.
When I lived in Florida, the Florida Turnpike (a toll road) used a card system instead of today's pay booths every few miles. The cards had different rates based on the number of axles on the car. A big-rig has 6 axles as opposed to a passenger car which has 2. A double big-rig has up to 9 (I'm thinking the cab has 1 front 2 rear, the load has 1 front 2 rear).
Certainly, a vehicle with 6 axles causes more damage than one with only 2.
-PJ