Power in Motion

Every time an underground train comes to a stop at a station it takes all of it's kinetic energy and transfers it into a lot of heat and noise in order to come to a stop. What would it take to create a simple regenerative braking system down there to harness that energy and put it back into the system?

I was thinking that if it wasn't possible to use the motors already on the trains for this then a simple generator attached to a tyre would do the trick. You could put one at every station entrance and as the train came in the tyre would push onto a plate on the underside of the train, thus causing it to rotate and generate energy in the form of electricity. This energy transfer would in turn slow the train down. If you cant picture what I mean then see the image below from the London Eye: