A rather clever way of capturing energy as vehicles slow down is to store the energy you'd use in braking as gravitational energy. This way of storing energy is used on a number of central London underground stations by constructing the stations at the top of a small hill in the track. Once built, the hump-back-station design has the handy effect of naturally slowing trains down as they approach a station and naturally accelerating them as they leave a station. Apparently, on London's Victoria line this saves 5% in energy and helps the trains run 9% faster.

You're not always going to be able to put a slope just where you need to slow down, unfortunately. However, it makes a ton of sense for pedestrian crossings where raising the crossing to the level of the payment means pedestrians don't have kerbs to negotiate and cars are naturally encouraged to slow down.

Victoria line data from Sustainable Energy without the Hot Air, by the late David JC MacKay

Hump-back stations

Best travel choices in London

Spent many battles with the London bikes before learning this simple trick.

Release Boris Bikes with ease by pulling up on the saddle

This handy tip from @inventor_tom. People who halt progress at the barriers are not easily tolerated here it seems.

Scan your Oyster card while walking to avoid angry Londoners

Because there’s only one way out and it’s a long walk and wait for the lift otherwise.

London sketches