Piezoelectric sensors are being tested for collecting traffic data, including weigh-in-motion, measuring vehicle speeds, classifying vehicles by category and counting axles etc. There are two types of these sensors ? polymer and ceramic. Currently WIM systems use a piezoelectric polymer sensor that produces a voltage proportional to an applied pressure or load. The polymer sensors are usually in the form of a long tape or cable embedded within a long block of elastomeric material. These blocks are installed into grooves, which are cut into roads perpendicular to the traffic flow.