beatle
Active Member
Here is another page regarding the 4th power rule and calculating road wear with more details about how it isn't a one-size-fits-all:That chart is simply using the 4th-power rule with 4000lb = 1.
The 4th power rule is the idea that damage to the road is based on the 4th power of the vehicle weight.
However, that's an oversimplification.
The actual 4th power rule is, I believe, closer to: the amount of damage done is proportional to the 4th power of the excess axle weight compared to the load-bearing weight of the road.
So, a moderately loaded big rigs won't do much to an Interstate, but would obliterate your residential street.
Similarly, light vehicle weights don't really matter much as the roads are built to take much higher weights.
And of course there's other damage. Our big winter problem is frost heaves which happen when there are large temperature swings.
How Much Damage Do Heavy Trucks Do to Our Roads?
(Inside Science) -- It may be obvious that heavy semitrucks stress and damage roads more than the average commuter sedan does. But by how much? Since the 1960s, the Generalized Fourth Power Law has been used as a rule of thumb when considering the relative damage done to the pavement depending...
www.insidescience.org
Agreed that there are other factors that have nothing to do with vehicle-caused road wear. This calculation, like many tax laws, is an oversimplification of an idea in an attempt to levy taxes on those who most benefit or depend on their collection for some publicly funded service. If the tax were easy to calculate and everyone agreed on it being fair, it just wouldn't be America!