For most of the more down-to-earth questions, I made the distinction between something that aids a human in moving by augmenting their analog output, and something that either doesn't require much human involvement to move or supplants it entirely.

Skateboards, rollerskates, wheelchairs, bikes, wagons, parachutes etc.. require constant human involvement to keep acting as a vehicle. Horses, cars, space stations don't really require the same involvement, or aren't necessarily exclusively human transporters, and toy boats are only facsimiles of vehicles.