Road Wear Explainer
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As far as the roads are concerned, the difference in weight between any two passenger vehicles including light-duty trucks, EV or ICEV, is negligible. These are all vehicles that generally weigh no more than 3 tons or so.
The difference between any two vehicles in this weight class is utterly insignificant regarding road wear compared to what causes the most road wear.
Straight box trucks (similar in size to U-Haul rentals) and especially tractor-trailers (the typical 18-wheeler) do far more damage on a per-vehicle basis than any car or light-duty truck than what its mere weight alone might indicate.
How is that?
You might think that a vehicle weighing 20 tons does 10 times more roadway damage than one weighing 2 tons. I mean, it makes sense, right? It's 10 times heavier.
But that would be wrong. And here's why.
Road wear is determined using the "fourth power law" applied to the axle load -- the weight each axle is carrying. That means when a weight loading on an axle is doubled, the stress on the road increases 16 times! Not simply doubled as you might think.
In short, the stress/damage caused to the road increases exponentially, not linearly, to the weight on the axle. So at larger weights, the stress/damage index increases very rapidly.
The loaded weight of a 26 foot straight truck (Similar to a larger U-Haul truck) can reach 32,000 lbs, give or take.
The legal maximum weight of a non-permit tractor-trailer rig is 80,000 lbs. Even an empty tractor-trailer (deadheading) weighs approx. 35,000 lbs. And with a permit, carrying special loads, weights can reach the low to mid six figures – well over one hundred tons.
Here is the axle weight loading and the stress it places on the road. We'll assume an even weight distribution among the axles for all vehicles except 18-wheelers.
1 (ton) raised to the 4th power ∝ 1 (unit of stress) This is our baseline.
Here's the full list from 1 to 10 tons weight load per axle. ^4 means raised to the 4th power
Axle Stress
Tons Index Notes
1^4 = 1 Baseline from which comparisons are made
2^4 = 16
3^4 = 81
4^4 = 256
5^4 = 625
6^4 = 1,296
7^4 = 2,401
8^4 = 4,096
8.5^4 = 5,220 8.5t is the max weight per axle in a two axle tandem, typical for semis
9^4 = 6,561
10^4 = 10,000 10t is the max weight on a single, non-tandem axle
To obtain the total stress index for a vehicle, multiply the index by the number of axles. e.g. The stress index for a vehicle weighing a total of 4 tons would be 32. Each axle has 2 tons of load (16 stress) times two axles for a total stress of 32.
For a tractor-trailer, there are typically five axles, four of which are carrying the bulk of the cargo load. So at maximum weight of 8.5 tons per cargo-bearing axle, that would be 20,800 on the stress index plus another 1,296 for the steering axle.
That's just over 22,000 on the stress index so just over 11,000 times more road stress/damage than a typical 2 ton car.
Another way of saying that: A car weighing 2t can travel about 11,000 miles causing the same total stress/damage to the road that a fully loaded tractor-trailer causes in 1 mile. That's pretty interesting, yes?
Here's a graph plotting the curve of applied road stress as a function of axle loading weight. This is just a visual representation of the list of numbers above.
As you can see, the line is pretty flat until the weight loading per axle surpasses about 3 tons. After that, every additional ton makes a larger and larger difference.
There are a lot of 18-wheelers on the road. If you've driven on any stretch of interstate highway, you can readily see how numerous they are.
So now you know! The vast majority of road damage, well over 90% easily, is caused by big rigs. And not by EVs or any other passenger car or light truck.
TO BE CLEAR, I am not throwing shade on big rigs, the people who drive them, or their importance to our economy. I'm stating neutral facts, nothing more.
n.b. The stress index is mostly meaningful when used as a comparison between two different axle loadings.
The fourth power law as it applies to road wear is not perfect. There are factors such as pavement type, temperature, subgrade conditions, and failure mode that affect its accuracy. But it has held up pretty well since it was empirically observed and findings published in the early 1960s.
My data comes from The American Association of State Highway and Transportation Officials (AASHTO) and the Federal Highway Administration (FHWA) pavement design guidelines.
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Graph showing stress induced to the roadway as a function of tons per axle.
Horizontal scale is load per axle in tons, Vertical scale is the stress index