I n t e l l i g e n t T r a n s p o r t a t i o n S y s t e m s one of China's most prosperous regions, has significant transportation problems. Continually deteriorating traffic conditions are leading to increased pollution, decreased worker productivity, and billions of dollars in costs each year. Recent improvements such as new highways and more lanes on existing roads have alleviated traffic congestion considerably. 2 However, incremental solutions aren't keeping pace with growing transportation demand. Intelligent transportation systems offer an alternative approach to solving many problems by implementing advances in information, Internet, communication, and cybernetics technologies.Ever more countries and regions are developing and deploying ITS subsystems and services. Considering the interoperation and integration required among different subsystems, many governments and organizations are working to establish their own national ITS architectures and standards for facilities and protocols that will bridge the gaps between subsystems. However, those architectures and standards don't answer some important ITS problems, such as how to integrate heterogeneous data on the semantic level, manage dynamic service flow, cooperate among different domains, and store and share massive data among different systems and departments. Solving these complex problems requires a fundamental shift in approach.Fortunately, the Grid offers a great opportunity to build a synthetic platform to address these issues. 3 Grid computing can support traffic data semantization, resource sharing, ITS subsystem cooperation, and global-scale distributed computing that connects all kinds of resources. 4,5 We are currently using grid technology to build DartGrid II, a semantic ITS platform to support resource sharing, service flow management, and cross-domain cooperation. Figure 1 shows the DartGrid II multilayer architecture. Its five layers address resources, basic services, advanced ITS services, ITS subsystems, and ITS applications.
Multilayer architecture
Resource layerThis layer provides data resources to upper layers. It divides resources into two categories:• Physical resources include terminal equipment: sensors, detectors, controllers, and any other facilities installed in roads, freeways, and vehicles. This equipment collects information such as dynamic and realtime traffic, weather, geography, and road conditions. • Logical resources consist of various databases and file systems, such as a vehicle database, driver database, and e-map file system.Collecting data from these resources requires consideration of their different access interfaces, data formats, and distinct communication protocols.To resolve this issue, DartGrid II encapsulates the resources in uniform grid services, which we define as any kind of grid resource that has a standard access interface and communication protocols.
Basic service layerThe next layer provides secure, transparent, and semantic-based data access, sharing, and management on which W ith increasing...