The Architecture View
The architecture view is an interconnected presentation of all of the components of the National ITS Architecture. A variety of entry points allow you to start with any of these components. Once in, you can easily navigate from component to component to find what you need. This view of the architecture is possible because of the traceability that is maintained between each of the architecture components.
The National ITS Architecture is comprised of three Layers. The Institutional Layer includes the institutions, policies, funding mechanisms, and processes that are required for effective implementation, operation, and maintenance of an intelligent transportation system. The Institutional Layer is shown as the bottom layer because solid institutional support and effective decisions are prerequisite to an effective ITS program. The Transportation Layer is where the transportation services are defined in terms of the subsystems and interfaces and the underlying functionality and data definitions that are required for each transportation service. This is the heart of the National ITS Architecture. The National ITS Architecture focuses on system integration and system integration requires effective communications. A general description of the communications services and technologies that support ITS is defined in the Communications Layer.
User Services describe what the system will do from the user's perspective. To date, thirty-three User Services have been jointly developed by US DOT and ITS America with substantial stakeholder input. A set of requirements covering each of these User Services are the basis for the National ITS Architecture definition. The User Services entry point leads you to the full set of user service requirements and allows easy traversal between the user service requirements and the components of the architecture that satisfy these requirements. Like other requirements, the user service requirements originate in the Institutional Layer.
The Logical Architecture defines the Processes (the activities or functions) that are required to satisfy the User Services. Many different Processes must work together and share information to provide a User Service. Data Flows identify the information that is shared by the Processes. These Logical Architecture entry points lead to ordered lists of processes and data flows and also allow access to data flow diagrams that provide a graphical view of how the processes and data flows fit together.
The Physical Architecture forms a high-level structure around the processes and data flows in the Logical Architecture. The physical architecture defines the Physical Entities (Subsystems and Terminators) that make up an intelligent transportation system. It defines the Architecture Flows that connect the various Subsystems and Terminators into an integrated system. The subsystems generally provide a rich set of capabilities, more than would be implemented at any one place or time. Equipment Packages break up the subsystems into deployment-sized pieces. Behind these entry points are the complete definition of the Physical Architecture. By following the links, you can traverse between the physical architecture structure and the related process and data flow requirements in the logical architecture.
Security is an intrinsic part of the National ITS Architecture. Services are provided that improve the security of the surface transportation system. The ITS components must also be secured so that ITS applications are reliable and available when needed.
Service Packages represent slices of the Physical Architecture that address specific services like traffic signal control. A service package collects together several different subsystems, equipment packages, terminators, and architecture flows that provide the desired service. The Service Packages entry point leads to a menu of service packages with underlying graphics and definitions. By following the links, you can traverse to the physical and logical architecture components that are associated with each service package. A theory of operations for each service package provides a narrative description of how each of the components support the service.
Standards: The National ITS Architecture is a reference framework for the development of Standards. The Logical and Physical Architecture provide a starting point for ITS standards development activities by identifying the applicable architecture flows and data flows to be standardized in the National ITS Architecture and the way in which the information is exchanged across those interfaces. The Standards entry point leads to an overview of the ITS standards activities and their relationship to the National ITS Architecture. Application Areas represent deployment-oriented categories of ITS Standards and are useful to deployers who wish to select only those ITS standards relevant to the services or systems they plan to deploy.