WIM System Components
In general, a complete WIM system includes:
- A set of weighing sensors, either mounted in the pavement (In-road sensors), or attached to a bridge (B-WIM). For on-board WIM, the sensors are installed on the vehicle. Additional sensors (e.g. induction loops) are mostly used to measure vehicle speed, length, wheel transverse location, etc. Road sensors can be scales, plates, strips or bars mounted inside the pavement, and sometimes mats or strips attached to the pavement surface. Strain transducers or strain gauges are most commonly used for Bridge WIM installations. Strain gauges, load cells, pressure transducers, accelerometers, displacement sensors, etc. are used for on-board weighing.
- A road side unit – or central vehicle unit – containing all the electronics including a data acquisition tool, data processing unit with software for weight calculation, (self-) calibration tool, user interface, a data storage, power source and communication devices.
- Other sensors or measuring systems: depending on the WIM technology and application, various additional sensors may be added and linked to a WIM system, such as temperature and deflection sensors to compensate variation in the sensor response, or cameras for overview pictures and license plate recognition for enforcement.