Piezoelectric roads are roads which convert the mechanical energy into electric energy.
Example : If a car is moving in the street from the it produces some mechanical force in the road, I the piezoelectric sensor will convert it into electrical energy which is used in street lights, traffic lights etc.
It's main aim is to utilize energy executed from the moving vehicles to replace fossil fuels in street light, traffic lights etc.
It is pollution free and can generate endless amount of energy and power.