I saw a fellow in one yesterday on The Blue (Southwark Park Road). It had 4 wheels, about 10" diameter with grey rubber tyres. The wheels were on a subframe which allows them all to be on the ground, or to raise itself up onto its front wheels at which the frame folds the back wheels up and inwards so they are against the back of the chair and half way up.
It looked amazingly odd, I wondered if I was being affected the the smoke from "Brixton Herbs"! Presumably it has Segway type gyroscopic stabilisers, but whereas a Segway has all its weight down very low and with the weight of the driver also carried down to a low level, this fellow was fairly large and sitting up about almost 3 ft above the two side-by-side wheels, so a VERY high centre of gravity, an inverse Pyramid! He was stationary for a while, then trundled off under total control and stability.
What a brilliant use of gyroscopes! Enabling a disabled person to converse almost normally with standing people, to see over shop counters and pub bars, to be more visible and "on-the-level" among other people.
