This article describes the ALFRED system for road surface condition measurements, which is applied by the Norwegian Public Roads Administration. Data collection for the system is performed by monitoring vehicles equipped with: (1) a dual beam of ultrasonic transducers; and (2) a sensor unit, carrying gyroscopes, accelerometers, inclinometers, and a laser distance sensor. The beam at the front of the system measures the cross profile. The instrument computer calculates cross profile, cross-fall, horizontal radius, longitudinal profile, travelled distance, and speed. It also calculates IRI, rut depth position and statistics, in real time, to provide running information to the system operator. It presents average values at the end of each measured 20m road segment, calculated from default 1m intervals, to enable the operator to make a brief judgement of the quality of the recorded data. These values are transferred to a surface condition database in the central RDB database of Norway. The whole Norwegian road network of about 32,000km is measured every year, including the initial condition status of about 5000km of new surfacings; the data are used for maintenance planning. A digital video camera system photographs the road surfacing and geometry every 20m. ALFRED has a quality assurance system, and is being enhanced.
Abstract