Wireless monitoring of highways

Electronic hardware has been developed to telemetrically transmit temperature and strain measurements from within a public highway in the UK. These measurements provide an important health check for monitoring fatigue damage in pavements. Previous attempts at measuring strain and temperature have required lengths of cable to be installed in the highway. The installation of these cables is both expensive and damaging to the pavement and provides potentially unreliable electrical connections. The new system consists of a retrofitted instrumented asphalt core which is bonded into the pavement structure. The core contains all the electronics necessary to record two temperatures (surface and roadbase) and two strains (longitudinal and transverse). An analogue front end provides signal conditioning which is digitized and passed to microcontroller for encoding. From here the data is transmitted via a low power radio link to a receiver and data logger positioned by the side of the road. The system has an in-situ operating life of 6 months on AA alkaline batteries. Results are presented of power management and fault tolerant radio protocol techniques, long term temperature variations, dynamic strain measurements within the highway, and RF transmission capabilities through a layer of asphalt.