Advanced Cruise-Assist Highway System (AHS) aims at remarkably safer and comfortable cruising and a sharp reduction in collisions by providing information on invisible obstacles ahead, intersecting vehicles, road surface conditions, etc., not possible in the past, to the driver in real time through the use of information and communications technology. The user services of AHS include (1) support for prevention of collisions with forward obstacles, (2) support for prevention of overshooting on curve, (3) support for prevention of lane departure, (4) support for prevention of crossing collisions, (5) support for prevention of right turn collisions, (6) support for prevention of collisions with pedestrians crossing streets, and (7) support for road surface condition information for maintaining headway etc. This paper reports the results of performance evaluations, plans and philosophy for improvement and future development issues for the following four fields as the key technology for realising these services: (1) Road condition sensors for detecting vehicles driving on the road, obstacles, etc.; (2) Road surface condition sensors for measuring the road surface conditions (dry, wet, water film, snow-covered, frozen, etc.); (3) Lane markers and detection systems for accurately judging vehicle positions and preventing lane departures; and (4) Road-to-vehicle communication systems for transmitting information such as sensor information, vehicle position information, and cruise-assist information in real time between infrastructure systems and vehicles. Further, the information gathered by those sensors can be used not only for AHS, but also the user services defined in the ITS system architecture, such as improvement of travellers' information, support for road management and maintenance, support for road management in the winter season, etc. So a report on the results of a study on the deployment strategy of multifunctional use of these technologies will be given provided with overall road infrastructure.
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