What about vehicles like cars? What types of things might have to be considered?
Well, chairs would have to have tail holes.In general, you'd have to make the inside of the vehicle adaptable to those riding in it. A Bear or a horse is going to need a lot more room then a Mouse, but if Mrs Mouse wishes to transport her friend, mr horse, the Vehicle would have to be able to accommodate both.
I agree, adjustable seats is a must. Seatbelts are easy to adjust, thankfully. I can also see the need for adjustable pedals and mirrors, though I can also see cars that are simply "meant" for larger or smaller species. Now, for racing helmets, I can see them just going to "Here's one for Ratlings, here's one for foxes," and so on.