A parking sensor, buried in parking spaces can detect the arrival and departure of vehicles, providing accurate information about available parking spaces. The Waspmote-based Smart Parking sensor is from Libelium. The company argues that accurate information on where to find available parking spaces helps traffic flow better, as well as decreases congestion. The sensors can be buried in parking spaces and communicate with the rest of the sensor network using Waspmote's ZigBee radio. The sensors communicate with their gateway via radios at either 2.4GHz or 868/900MHz. For 2.4GHz ZigBee connections, mesh networks are implemented with routing motes located in street lights. For the lower frequency radios, it is possible for parking sensors to communicate directly with the gateway as the propagation distance is longer. One benefit of the radio, according to the company, is that its power management and over the air programming mean that, once installed, parking sensors do not need to be accessed for years. Over the air programming enables the software for networks to be upgraded over the radio network without digging up the parking spaces. Sensor nodes are supplied in a PVC casing rated at IK10 for mechanical impact protection and at IP67 for ingress protection. The use of PVC ensures that radio communication is not hindered.
