In southern Europe, motor scooters and light motorcycles are a substantial part of the transport mix. Scooters are a fast, economical, traffic-beating option. With fuel at over $8 per US gallon, a 100mpg scooter has tremendous appeal. It's quite common for dad to ride a scooter to work, while mum takes the kids to school in the car. A young adult is just as likely to start motoring on a scooter as in a car; Towns and cities in Spain and Italy are overflowing with scooters on weekend nights. Most of those towns were never designed for cars and have a desperate shortage of parking - you can get five or six scooters into one parking space.

A vehicle like this has most of the advantages of a scooter, without the obvious shortcomings. It could fill the same role in the vehicle mix in countries where weather, safety concerns or cultural factors make motor scooters unpopular.

Most car journeys involve a single occupant. That's a luxury we've been able to afford until now, but lugging around four empty seats is seeming ever more wasteful.

If it were much, much cheaper, a one-seater plus room for groceries would make a fine commuting vehicle.

The problem, as always, is cost. My family manages with one vehicle plus public transit, but that vehicle has to be big (people and cargo and distance). Most of the time we could use something smaller, but the minority use case is enough to require the behemoth.

If it were cheap enough, we could really use three vehicles: a commuter, an efficient four-seater, and a seldom used cargo/distance vehicle. That's not how the economics work out, though, so one vehicle has to serve all the purposes.