Originally Posted by
nfmisso
If you go to the heaviest of land based transport systems (freight railroads), you will find "Dynamic Brakes"; which use the traction motors as generators dumping electrical power into resistor grids (toaster wires), generating MegaWatts of heat and drag. Why do railroads use this technology - overall it is cheaper than totally relying on friction brakes.
Sure, but that's because of the magnitude of the energy they need to disperse - spreading out the heat to a large area with a resister grid is an efficient way to do that.
But, as already mentioned by Leisesturm, there are reasonable mechanical methods available that do an adequate job handling the heat generated by bicycle (either single or tandem) brakes and these have the advantage of being simpler (more reliable), lighter, and less expensive than an electrical regenerative system.