That 4th power law works both ways. A 40 ft bus 2 axle bus with 80 passengers will weigh about 40 000 pounds. The axle weight is 20 000, so by the 4th power law the damage is proportional to 2 x 20 000^4 = 3.2 x 10^17.
If instead those 80 passengers each drove alone in a Kia Niro EV it would be about 4 000 pounds each, so an axle weight of 2000, so the damage would be proportional to 160 x 2000^4 = 2.56 x 10^15.
That's 125 times less road damage than the bus!
Another interesting 4th power calculation is EV vs ICE. My car is available as an ICE, a hybrid, or an EV. I've got the EV which weighs more than the ICE.
Based on the 4th power law I should be doing about 40% more damage than I would if I had bought the lighter ICE model.
But wait! With the ICE model I'd need to regularly by gasoline, and that gasoline is delivered by a tanker truck. Tanker trucks, especially when they are traveling between wherever they load and wherever they unload, are very heavy.
I calculated what would happen in a hypothetical city where everyone drove the ICE version and then all switched to the EV version, and how many tanker truck gas deliveries that would eliminate. I don't remember the exact numbers but it was something like if mid sized tankers were used for gas delivery then if they had to drive more than a few miles from wherever they loaded up to wherever they unloaded the elimination of those trips by everyone switching to EV would reduce road damage by more than the damage caused by the EVs being heavier than the ICE cars.
> A 40 ft bus 2 axle bus with 80 passengers [...] If instead those 80 passengers each drove alone in a Kia Niro EV
Bzzzt. Wrong, unless you literally have a bus that goes from A to B without stopping. City buses do not carry "x passengers", they serve trips. An 80-passenger bus serves way more trips than 80 (though not on average of course), as people can freely get on and off at any time.
And of course, there are way more aspects of this problem than just road wear, parking space for one.
But sure, we absolutely should put buses on rail tracks!
Thank you for doing the calculations. This is interesting and useful. Yes, people should switch to EVs, but mostly because it helps build resilient independent grids (eventually), EVs add a layer of energy storage, we can dump excess energy when its negatively priced (or free) and supply power back to the grid when its costly, replacing peaker plants.
I wasn't talking about passenger buses, because thats unlikely going to happen in US. Almost all of damage is done by 18-wheelers. A fully loaded 18-wheeler: 80,000 lb. Everytime a discussion comes on ICE vs EV, the fossil fuel proponents immediately jump to but EVs weigh more (debatable) and cause more damage. The damage they cause is insignificant compared to 18-wheelers. I'm not entirely sure if EVs weigh more either, maybe the earlier models did, but energy density keeps increasing. Also, there is no compelling reason to have 300+ mile range batteries when most of the trips are under 3 - 5 miles.
If instead those 80 passengers each drove alone in a Kia Niro EV it would be about 4 000 pounds each, so an axle weight of 2000, so the damage would be proportional to 160 x 2000^4 = 2.56 x 10^15.
That's 125 times less road damage than the bus!
Another interesting 4th power calculation is EV vs ICE. My car is available as an ICE, a hybrid, or an EV. I've got the EV which weighs more than the ICE.
Based on the 4th power law I should be doing about 40% more damage than I would if I had bought the lighter ICE model.
But wait! With the ICE model I'd need to regularly by gasoline, and that gasoline is delivered by a tanker truck. Tanker trucks, especially when they are traveling between wherever they load and wherever they unload, are very heavy.
I calculated what would happen in a hypothetical city where everyone drove the ICE version and then all switched to the EV version, and how many tanker truck gas deliveries that would eliminate. I don't remember the exact numbers but it was something like if mid sized tankers were used for gas delivery then if they had to drive more than a few miles from wherever they loaded up to wherever they unloaded the elimination of those trips by everyone switching to EV would reduce road damage by more than the damage caused by the EVs being heavier than the ICE cars.