Hi,
  last month I have been thinking about the wasted energy decelerating vehicle and regenerative breaking. There are good and viable systems around to recover the energy from cars by means within the car. However, I was and still am intruiged by the notion of recovering energy using the road surface or other means.

  At the time I considered traffic lights, intersection and off ramps on motorways to be a good place for implementing such devices.  Now I would like to consider the use of regenerative breaking at stop signs. The main advantage of a stop sign is that all cars must break at this place. Every car must come to a full stop. A regenerating road surface, such as a slight ramp that uses the weight of the vehile will not only provide a means of recovering some of the kinetic energy but also improves road safety be delaying quick progress at this point, i.e. running the stop sign.

  My favorite mechanism at a stop sign is likely to be a ramp. It normally is in the upper position requiring the vehicle to traffel upwards onto it. Whilst the ramp then sets to its lower position the car must be required to stand before continuing. Once the car has left the ramp sufficient time needs to be given to the following car for the ramp to raise up again. This is dependent on the travel distance of the ramp but should be small. Hence, unlike all other places, the ramp will be actuated for every car.

  Considering the ramp for a moment, I envisage a mechanically raised large sheet of metal lifting a total of 2-3 cm up from the road surface either using pneumatically or hydraulic system. The passing car pushes down the ramp and by driving up the ramp transfers some of the energy to the system. It is also store for the lifting action once the car has left the ramp.

  For safety reasons the travel distance must be small else to avoid creating a tripping hazzard or possible damage to vehicles reversing for whatever purpose over the ramp. Smaller travel distances mean more force needs to be transferred and thus the mechanism becomes slower.