Rough terrain with less and less purchase, until it just turns into a pile of dry dust / wet mud (depending on weather). A legged vehicle as heavy as a car would wear away stone, tear roots… I don't think there's any surface that could withstand heavy traffic, except maybe something ridiculous like a fast-growing woody grass.

For some reason, I was imagining a machine with legs like a footstool. Any realistic machine like this would have large, wide feet. With proper suspension, the pressure might be low enough to not completely destroy the ground.

Though, I'm struggling to see how this would be better than a wheeled vehicle: you've still got static friction between the feet and the ground… I guess maybe they're flexing less?

Yeah, large feet would reduce the pressure on the ground, though it would still suffer some effects for sure — but the goal is to avoid rubber and microplastics, so metal feet it is :)

Anyway, I agree that a wheeled vehicle is probably going to win on efficiency just the same, though wheels do require better roads than legs do (eg. common example is stairs).

A bicycle can do stairs just fine. They're tricky, but not much more than a similarly-steep hill would be. (Of course, that's ignoring wear on the tyres from going over the edges of the steps.)

With wheels, it depends on the size of the wheel what unevenness in the terrain it can cover.

Eg. a monster truck can handle more of it, but it's impractical for a bunch of other reasons.

Similar holds for legs, but legs can usually do jumps too.

> one big upside is that you can theoretically avoid the rubber/microplastic particulate emission associated with tires and wheeled vehicles if you can make legged vehicles as good as wheeled ones.

How does keeping rough terrain rough help with that?

My implication is that you want rubber for nice asphalt/road surface to avoid damaging it — for comfort, other suspension components can help out instead.

If you don't care about preserving the terrain (which you can when it's rough to begin with), you can just go with large surface metal feet and you should not get any rubber/microplastics, though you will get metallic dust.

Wht do you think mountain bikes have rubber tires? Or one of these? https://en.wikipedia.org/wiki/All-terrain_vehicle Or a dune buggy?

Pretty clearly the worry about the road surface is not the only cause of using tires.

Also, if you don't care for either preserving the surface or comfort (use something else for comfort) then... use metal wheels. Or ceramic wheels, or tracks or something.

I believe the main issue is the rubber and chemicals from the nice road surfaces. So your argument seems like a problem looking for a solution?

That's wrong: the problem is the rubber on the wheel (or feet in case of legs) being spent due to the traction and emission of rubber microparticles as it is.

Yes sorry I wasn't clear enough. Rubber and chemicals from tires on the nice road surfaces. That's what that should have said.

But the legs are still a solution in search of a problem.

Sure, the original article is about a legged movement, and the entire thread is about microparticle (plastics/rubber) emission comparison between wheels and legs.