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In road traffic management, the provision of up-to-date, accurate and detailed quantitative information on traffic movement is essential. Road Traffic Monitoring by Satellite (RTMS) is a satellite application, which monitors a small population of the traffic with on-board equipment. This fleet flows with the traffic, records traffic speeds, detects congestion and reports this via the satellite to a central system. The objective of the project is to design such a system, to implement it on a limited scale and to practically demonstrate the concept's viability in a field trial.
In order to make a system economically feasible, the functionality of gathering traffic information can be combined with a myriad of other services, such as route guidance, location based services, emergency services, vehicle tracking and tracing. The traffic monitoring system consists of mobile systems, mounted in cars or trucks, and a central server. The system was designed using existing satellite communication equipment. The in-car part consists of a GPS receiver, software and a two-way satellite communication system. The software matches the vehicle positions on a road map, determines the driving speed for each road segment, and detects traffic events. The central part consists of the satellite communication part and a communication manager, which manages the fleet. 
In the first phases of the project, the services and system were defined. A communication protocol was defined specifically for traffic monitoring by satellite. Then, a pilot system was designed, built and tested. A small number of systems were installed in a test fleet of mostly trucks, which were operated intensively in a relatively small area around Rotterdam, NL. Data were gathered and the ability of the system to detect traffic events and communicate them effectively and efficiently were assessed. 
One of the major challenges is to make optimum use of the limited data rates available on the return link of the satellite communication. This raises two key issues: first, a smart communication protocol must be designed and second, intelligent on-board software must be made, software which is able to automatically detect traffic events such as congestions.
The field trial has shown that the mobile systems were able to detect traffic congestion and to communicate these events, even in urban areas. Satellite-based traffic monitoring has advantages over conventional systems such as loop detectors and ground-based video cameras, because satellite systems potentially cover the whole road network - not just busy road in and around cities. Further, a system with probe vehicles provides travel times, where conventional systems only provide speeds at a single point. Travel times are much more valuable to both road users and road authorities.
The project was finished with a successful field trial in October 2002. A further study is under consideration.
Last Update: 08 Nov 2006
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