Isn't there some way to take advantage of the energy and motion of the traffic on freeways?

Question

Don't know if this is the right category, but I was coming home from Los Angeles, on the freeway tonight, and I was thinking: "Why can't someone install a bunch of hardly noticeable rollers, spaced maybe a half-mile apart, in the pavement, hooked up to harness electricity from the heavy traffic. It seems expensive to install, but then it would be free energy! The cars are going to travel on the freeways anyway, so why not use the energy and motion they provide. So.........tell me how stupid this is. I'm totally ignorant of engineering, so it could be impossible and I wouldn't know!

Answer 1

Theoretically, there is no such thing as free energy.  What that means is that the amount of energy created by the rollers would be less than what it cost the vehicles making the energy to spin the rollers.  Not to mention the initial investment of installing the rollers.  If your theory was true you could use a car to spin rollers all day long and create energy, except it would take more energy to spin an engine that long.