I had this exact idea (solar + piezo) as a freshman EE student about 12 years ago though I imagine someone else had it long before that.

I'd be concerned that gas mileage of the automobiles would be reduced by the extra "work" cars would do "straining" (eg pushing down) the piezo-electric generator. Here's why: for every piezo-electric generating location that's pushed down ever so slightly, the car will have to drive back "up" to road level. The result may be that gas mileage for cars will be reduced as though the cars were driving slightly uphill the entire time.
Perhaps an analogy will help: Turnstyles can generate electricity, but you wouldn't install them on a marathon route because it it's too much "work" for the runners to go through them. Similarly, the cars would be doing "work" (generating electricity) to activate the piezoelectric generators.
Here's the exception: on a steep downhill section where cars are usually on their brakes, a piezo-electric generator would work well for all but the hybrid and electric cars.

The solar panels sound interesting , my only concern is how well the glass surface holds up. Cars skid, crash, and burn. often scars are left in the tarmac as a result.

That road surface has to be some kinda super tough glass to hold up to the punishment of use.

Using piezoelectric roads to generate electricity would have the net effect of using gasoline to generate electricity with a very inefficient engine. The only way it would make sense is if our roads might could designed to intentionally waste some energy for safety reasons, but to my knowledge, that would only make sense in spots where you wanted drivers to slow down, like with rumble strips and whatnot. Maybe you could put piezoelectric under off-ramps and such, but then cars with regenerative braking have their recoupment wasted.

Solar roads make very good sense though, in principle.

Rolf, fair thought but it's really not like a turnstile. It's downward pressure being used, not horizontal. The downward pressure is overwhelmingly provided by the car's mass, not the engine. The extra power used by the engine is tiny compared to the pressure received by the generator. In other words the tradeoff is thousands of times any extra fuel used.

Good idea ... use "Piezo" ...

Andrew, conservation of energy states that any energy generated by the road must come from some where. A car sitting on a piezo-road produces no electricity - It is only when the car imparts force on the road, and compresses the piezo by some distance. (You know, work is force x distance). The only thing in a car that generates energy is in the engine, so there is your source.

This is all a pretty bad idea. Combustion engines are very inefficient, so we dont want them generating electricity. And solar panels under the roads sounds like a maintenance nightmare. Even if you where in a place where land is at such a premium you could afford to put solar panels under the roads, isn't it likely that the traffic would be covering the panels most of the time?

There is no alternative or clever solution to the brutal reality that we as a society use many orders of energy more than we can sustain. You would need 350 million m^2 of those solar panels (which produce 50kWh/yr) to equal *one* Indian point. And that is only 5% of new york state's peak load.

GW reported: “The idea is pretty straightforward: a layer of concrete forms the road itself. A centimeter thick layer of crystalline silicon solar cells is laid on top, and covered by a layer of toughened glass. The energy potential: 50kWh per square meter per year, which can then be used to power street lighting, traffic systems and households”.

The average retail price for a kWh of electricity in the US is .10 cents per kWh; the average wholesale price is .05 cents, so 10.76 square feet would produce $5.00 retail or $2.50 a year of wholesale electricity. Ha. Ha. Sounds like a real money maker to me but if you keep the glass clean for the solar electric system to work, you have a glass slick road!

Solar dc electric means that it only generates electricity when the sun shines on it, and Oh, what about the batteries that are not mentioned to operate the street lights at night? They must be quite expensive. I hope they aren’t anymore than $2.50 a year! Ha. Ha.

The idea, from an engineering point of view, is so ridiculous that I am surprised it is not fully funded. Ha. Ha. It is a great diversion of thought from the greatest energy invention of this century the water/hydrogen cell and of its inventor Stanley Meyer.

Add on comment in defense of scientist Stanley Meyer’s invention of the water/hydrogen fuel cell and the campaign by the government, Banksters and Big Oil world corporate empire against Meyer’s honor as a scientist by discrediting his invention with slander and lies.

Indeed, their attacks are on SCIENCE and the advancement of SCIENCE.

Meyer’s invention with proven SCIENCE outmodes oil, gas, nuclear, solar and wind as a source of abundant, free, clean energy and would eliminate any man made global warming from the continued use of fossil fuels for energy and would eliminate the need for using dangerous nuclear energy for power.

Example of brainwashing Gnomes: Google “Stanley Meyer” and the first on the list is Wikipedia, the “honest, scientific encyclopedia” for the internet, right? Well yes and NO, on the important issues they are rabid political and anti-science with gotcha brainwashing for the unsuspecting Gnomes.

After reading the Wikipedia propaganda in its many false reinforcing forms, you will be thoroughly convinced that anyone who who thinks that you can burn water for fuel is crazy. Wikipedia will not even acknowledge that in order to receive a US patent that you first have to prove with empirical science the concept before the patent office will issue a patent. The patent office fought with Meyer every step of the way to receiving patents but Meyer, a great scientist and mind, was way smarter than any of them and forced the patent office to issue him his patents with SCIENCE proof of concept complete with working models.

Stanley Meyer is so important and dangerious that, I would say, at least 80% of the web pages naming him are disinformation sites to mislead and discredit water/hydrogen fuel cells.

H2O is water, one part hydrogen, and 2 parts oxygen. Hydrogen is 10 times more flammable than gasoline and 20 times more explosive.

Yes, a person can separate the hydrogen from the oxygen and burn the hydrogen. Yes, even a Gnome can build a water/hydrogen fuel cell with common hardware supply components and burn water for fuel. Yes, Wikipedia is deliberately lying to you!

Michael Raines at expert village will show you how to build a basic hydrogen fuel cell housed in water filter canisters that is not nearly as refined as Stanley Meyer’s end product, but close to Meyer’s original concept and proves that hydrogen can be separated from the oxygen in the water. Mr. Raines concludes in his experiment that hydrogen fuel cells are kept off the market by Big Oil and the government.

Michael Raines, expert village youtube 8 part series.
http://www.youtube.com/watch?v=KM4zT3SUO7Y

How about powering electric vehicles on highways with solar power. This could boost the use of electric vehicles as you will not have to "charge" it for 8 hours for using it

We could also power the vehicles on the road the same way like the electric trains are run