AHS ROAD SURFACE SENSORS

A full range of services are studied in this paper for use in Advanced Cruise-Assist Highway Systems (AHS) with the objective of improving traffic safety and increasing traffic efficiency. AHS road surface sensors have been under development since 1996 for the purpose of realizing the practical application of road surface condition detection sensors. These sensors are being developed for efficacious use both in detection of road surface conditions as required by AHS services and in management of road surfaces (snow removal operations, spreading chemical agents, etc.). Starting from 2000, in particular, the sensors have been installed on public roads and subjected to functional verification. This report will describe improvements made in sensor function on the basis of those verification results. Road surface conditions have a significant effect on vehicle behavior, and particularly on braking and steering. In the interests of traffic safety and efficient traffic flow, it is necessary to accurately detect surface conditions on the road ahead that vehicles are unable to detect, and to inform the vehicles of those conditions. AHS road surface sensors can be used on the one hand for providing reliable road surface information in real time, with high accuracy, and with a high detection rate, qualities required for AHS applications but which conventional sensors did not have. On the other hand, these sensors can also be used efficaciously for management of road surfaces and other functions of road management. Consequently, it is considered necessary both to clearly define the limits of detection performance of the sensors themselves, and to equip the sensors with self-diagnostic and other functions needed to assure their reliability.