No Geneva motor show would be complete without a crazy contraption bowled up by Swiss coachbuilder, Rinspeed. And this year is no exception with ‘Dock+Go’,  essentially a tri-axle version of the electric smart fortwo.

The third axle is an ‘on-demand’ affair that can be configured in a variety of ways and affixed when needed. One of the potential uses for the ‘backpack on wheels’ is as a range-extender, as the 100km-odd range offered by the standard vehicle obviously imposes severe limitations.

The caboose thus houses an ‘energy pack’ comprising additional batteries or a fuel cell or combustion engine that recharges the car’s existing batteries by driving the second axle.

To top it off, when the pack with auxiliary batteries is docked and the vehicle is not in use, the pack can provide electricity to the owner’s private residence or serve as a buffer for the public energy grid, in effect turning it into a ‘smart grid’. And the fact that the extra batteries or range-extending combustion engine are only carted around when needed eliminates the efficiency drain imposed by the added weight of the former, so the set-up effectively offers “mobility a la carte”.

Alternatively, a different pack can turn the electric flea into the dream car of every pizza delivery driver – complete with a built-in heated box. Another potential use is for winter-sport enthusiasts to use the pack to stow all their gear.

The Geneva show car, however, has been configured as a rolling “sound pack” that multimedia and infotainment specialist Harman has filled with the latest high-end audio gear to make it a virtual mobile disco.

Rinspeed boss Frank M Rinderknecht perhaps best summed up the ‘backpack on wheels’ concept with the following remark: “You’re not going to take your steamer trunk as if you were going on a lengthy vacation if all you want to do is a little shopping at your local supermarket!”

Makes sense to us… which leads us to believe the Rinspeed folks aren’t nearly as kooky as we gave them credit for.