Without much better data the best you can say is that Ubers are benefitting from externalities at a rate lower than other, heavier vehicles. It's still likely they aren't paying their fair share.
A road that's never driven on suffers damage from the elements, and the passage of time.
A truck does more damage then a car? Great. But there's an upfront road maintenance (not to mention construction) cost that you have to pay, regardless of who uses the road. Gas taxes do not come close to capturing that.
