Originally Posted by
Roody
You're missing the forest for the trees.
He may not be deep enough into the forest yet to see the real trees. My first question with regards to vehicles' impact on pavement relative to weathering and erosion is to ask what forces are going into the pavement from the vehicles. There are up-and-down 'bouncing' forces and the lateral forces of starting and stopping, and cornering.
When a crack forms in pavement, water is going to seep down into the crack and when the water freezes, it expands causing the cracks to grow. If two cracks are close enough to each other, lateral forces caused by a tire gripping as its vehicle accelerates, decelerates, and/or corners will break off the piece of pavement between the two cracks. Lateral forces may also cause the pavement surface to tear if it has room to be pushed.
Large, heavy vehicles like trucks may be responsible for more forces on the pavement, but cars are not too light and low-powered to produce strong shear forces when accelerating, decelerating, and cornering. The following quote is from
Studies on stress distribution in pavements subjected to surface shear forces
This implies that surface vertical force is responsible for failure of concrete pavements and that surface shear force contributes very much to the failure of asphalt pavements. This explains why the failure of asphalt pavements takes place very often at crossings and curved parts of asphalt pavements where high surface shear force is likely to be applied.
The article concludes noting the common observation of more damage at crossings:
It has been said that pavements at crossings as well as curved parts are subjected to surface shear force of which magnitude is similar to that of surface vertical force coming from the weight of vehicles. The results of this study shows that the maximum shear stresses brought about by surface shear force in the areas near the surface of the upper layers are higher than those by surface vertical force for lower Young’s modulus ratios which is the case for asphalt pavements. This implies that the effect of surface shear force should be carefully considered in designing asphalt pavements.
Ultimately, I think the bigger picture is that regardless of how little damage cars may do to the pavement, the sheer number of cars on the road causes congestion and multi-lane widening, as well as sprawl; all of which drive up the total cost of infrastructure. If weather is indeed the main factor in road deterioration, then the main concern should be with minimizing the total surface area of roads. This isn't even taking account of all the tree-displacement and land-area that could be used for other activities besides driving and parking.
And then there's the problem of all the time wasted in driving around sprawling, congested road networks that could be spent in either economic pursuits or for recreation, family time, etc. We waste a lot of time, energy, and money consuming motor-vehicles and roads for the sake of fiscally stimulating the economy we're driving around in.