I've read about this same technology before used in a disco to generate the electricity for the lights. I wonder when the next logical and probably higher energy gathering step of generating the energy from vehicles driving will take place. Already a form of it happens when a hose is run across the road and as cars drive over it air is used to move a counter or ring a bell. When will that turn into something that generates enough power for a capacitor or charges a battery that is then used to run traffic lights. Cars weigh a lot more and heavily congested areas have more potential for generating electricity.