Piezo Sensors are an axle detection sensor that is installed in the roadway (mostly permanent but can be temporary). The sensor is embedded in the lane of travel and can collect count, classification, and Weigh-In-Motion data.

Typically a class I sensor is used for weigh-in-motion application while class II sensors are used to collect axle classification data.

Piezo sensors work by producing a signal (voltage and current) when an axle/tire comes in contact with them in the roadway, This signal is detected by the electronics in a counter/classifier.

The sensors embedded in the roadway are extremely accurate at measuring axles strikes. They are used in application for counting, classification (speed and axle), weigh-in-motion, tolling and even law enforcement installations such as speed and red light running.