Because that function is so convex, almost all of the cumulative damage to roads is done by lorries, buses and fuel trucks.
Cars, even big ones, are negligible compared to the fourth power of bus weight.
Cars, even big ones, are negligible compared to the fourth power of bus weight.
That’s an oversimplification, but it doesn’t really matter if it’s 99.9% or 95% of the damage ware is still absolutely dominated by heavy vehicles.
And it could be a lot more negligible, if that mostly drive alone, drove a car with half the weight.
I used 4,000lb for the car, a 2024 Chevrolet Suburban which is huge only clocks in at a 5,824 lbs. Load another 1,000lb for passengers etc and (6,824/4000) ^ 4 = 8.5x a car or 0.5% what I calculated for a full 18 wheeler.
Sure there’s more cars than 18 wheelers but 7,000lb is a rather extreme outlier in terms of SUV weight.
And it's probably heavier than most cars around here, because most cars are not 7 seaters, but 4/5 seat hatches.
US SUVs and pickup trucks wouldn't fit most parking lots around here (to tall, to wide to even get in), but somehow the problem is never the size/weight of cars people got used to drive.
It's not like they're the sum of all evil, they have a small impact on the size of these things, but bringing the sizes down will help on the pathway to lowering the size of everything.
The fuel trucks aren't going to change in size, they're going to come more often. Also, oil is typically distributed in pipelines or on ships rather than trucks until the last mile. Meanwhile a fuel tanker holds some 10,000 gallons of fuel, i.e. enough for "large" 20 MPG SUVs to go 200,000 miles. Meanwhile the tanker is generally transporting the fuel less than 100 miles, so this is diluted by a factor of 2000. Because of the 4th power law, this still causes nearly as much damage as the SUVs themselves, but they're both still negligible compared to all of the other commercial trucks transporting everything else.
Obviously this doesn't even apply to electric vehicles.
> They use more materials to make, require bigger places to store/maintain them and go through bigger consumables ie tires -> bigger lorries.
This is an even smaller effect than the fuel.
The US sells on the order of 4M domestically produced pickups and SUVs per year and produces 1.8MT of steel. If we, conservatively, reduced the weight of all of those cars by half or 1T ea (they're often 3x the weight of a sanely sized vehicle) we quickly eclipse US steel production, even if we exclude some parts as non-steel. That multiplies by 1.6x when you think in terms of iron ore (though most is recycled from scrap).
TLDR: go play factorio
But you want to optimize the thing where you get the most bang for your buck.
The heavy side of the most popular SUVs aren't based on the F-350, they generally weigh around 4500 pounds vs. 3500 pounds for the lighter end, the latter being around the same as the average mid-sized sedan. Cutting 30% off of a one-time cost for something that will have a 20-year lifespan is generally not going to be the best place to optimize.
Compare this to, say, introducing mixed-use zoning so people can live closer to their jobs and drive fewer miles. This not only reduces fuel consumption on an ongoing basis, it makes cars last longer because they have fewer miles on them and then you don't need to manufacture as many, and it has direct human benefits because people spend less time stuck in traffic and drive fewer miles with risk of traffic fatalities.
One of the roads up the mountain has switchbacks near the top that are so tight that nothing longer than 18 feet is allowed up, but at least 2x a week a box truck gets stuck.
Heavy cars have many negative impacts but road maintenance isn’t one worth worrying about.
At the extreme end, imagine a railroad bridge. We don’t care about how fat the mice that regularly cross it are.
None of those drive on small local roads, but mom trucks do.
A full sized school bus will regularly drive on just about any road. Fully loaded they’ll do 1000x as much damage as a large SUV.
Fire trucks, septic tank pump trucks, big furniture delivery trucks, landscaping trucks, motor homes etc… will also drive on pretty much every small local road.
And much bigger commercial trucks drive on very small local roads enough to dwarf the damage of a large SUV. My neighbor just had a foundation for an addition poured. 3 cement trucks came out. 3 fully loaded cement trucks would cause something like 20,000 times as much damage as a large suv.
I’d need to drive on my street once a day for 50 years in an enormous suv cause as much damage.
Given normal weathering and damage caused by frequent or even infrequent large commercial vehicles, larger local passenger vehicles aren’t going to increase maintenance costs.