Battery Electric Personal Tractor Trailer
This is the sort of electric "car" I wish they'd make. Batteries are expensive and heavy, so a relatively small short range battery would be most efficient and cost effective. A quick swap option would be nice for extended range.
Well, I'd like a quick swap where you swap a tractor unit that integrates batteries and two motorized wheels for propulsion and steering. That way, the passenger unit is just a trailer. The expensive parts - the batteries and motors - are in the tractor unit.
Most cars spend most of their time parked, of course. With this system, that means just parking an inexpensive trailer. The expensive parts can spend most of their time on the road or recharging.
A tractor trailer system isn't locked into one size fits all, the way a battery swap system is. It's possible to use a smaller unit for short range commuting and only occasionally use a larger long range unit for long trips to places without tractor swap stations.
It's also possible to have very differently sized trailers suitable for different needs. A one person or tandem trailer for commuting can have a lot less air resistance than a wider, bigger trailer suitable for a family trip.
