Does all that take into consideration the number of tires per axel, and size of the contact patch for each axel?
I would assume that road damage is proportional to surface pressure at the contact patch, so greater contact patch means less damage. As a result you can have a heavier vehicle do less damage than a lighter vehicle with the same number of axels, if the number and size of tires on the larger vehicle is greater than the smaller vehicle.
Most busses I see around run large truck tires, and normally have 4 tires on the rear axel vs the normal 2 you’ll find on a Hummer. So a bus spreads it weight over 6 tires rather than 4, and if we generously assume the Hummer tires and bus tires have the same contact patch, that means a bus can be 50% heavier than the Hummer, but not cause any additional damage.
I know loading regulations are normally done based on axel number, rather than tire number. But I assume that’s mostly down to ease of regulation, rather than axel count being the most accurate way to calculate road damage. Indeed the document you link too even breaks down loading limits based on number of axels, but also single tire limits, which maybe different depending on pressure of the tire.
Edit: I also note that U.S. buses seem to be much heavier than necessary. As a point of comparison a two axel double decker, New Routemaster in London[1], which carries up to 87 people, has a curb weight of only 28,000lbs, which would give it a fully laden weight of only 29,000lbs. That’s substantially less than equivalent buses in that document.
I would assume that road damage is proportional to surface pressure at the contact patch, so greater contact patch means less damage. As a result you can have a heavier vehicle do less damage than a lighter vehicle with the same number of axels, if the number and size of tires on the larger vehicle is greater than the smaller vehicle.
Most busses I see around run large truck tires, and normally have 4 tires on the rear axel vs the normal 2 you’ll find on a Hummer. So a bus spreads it weight over 6 tires rather than 4, and if we generously assume the Hummer tires and bus tires have the same contact patch, that means a bus can be 50% heavier than the Hummer, but not cause any additional damage.
I know loading regulations are normally done based on axel number, rather than tire number. But I assume that’s mostly down to ease of regulation, rather than axel count being the most accurate way to calculate road damage. Indeed the document you link too even breaks down loading limits based on number of axels, but also single tire limits, which maybe different depending on pressure of the tire.
Edit: I also note that U.S. buses seem to be much heavier than necessary. As a point of comparison a two axel double decker, New Routemaster in London[1], which carries up to 87 people, has a curb weight of only 28,000lbs, which would give it a fully laden weight of only 29,000lbs. That’s substantially less than equivalent buses in that document.
[1] https://en.m.wikipedia.org/wiki/New_Routemaster