russ_watters said:
Attaching a power generating device to the road therefore requires burning more gas.
Well it is far from being trivially as clear as you seem to suggest !
Take a fat trucker, you will not tell me that a bump on the road can not generate accelerations of the order of a few g, proof is as simple as him jumping from his seat now and then. Attach some kind of electrical generator to him, and you will definitely get some power out of it. Certainly not enough to light a bulb, but in principle at least it works, and in that case I do not think it affects the amount of gas burnt by the engine, at most it makes the trucker jump less high.
Therefore, I imagine it possible indeed to use the same kind of generator to the road, possibly not affecting the gas at all, but
reducing the stress in the shock absorbers for instance, as Ivan mentioned.
As I said before, I have put an accelerometer in a truck, so I have measured those vertical accelerations, I am aware they are very short, but I was amazed how high they can reach.
Finally, I mentioned the fact that the whole thing would probably affect the number of miles per gallons (said "increase" instead of decreased BTW). I just can not provide actual numbers, and that was all just merely out of fun if you really read what we've been exchanging here.
edit
I did not see your second post before I started this one
