Subsystems & Terminators
Subsystems are the principal structural element of the ITS architecture and represent the individual pieces of the intelligent transportation system. They are grouped into the following four classes:
Centers - Subsystems that provide management, administrative, and support functions for the transportation system. The center subsystems each communicate with other centers to enable coordination between modes and across jurisdictions. Some examples of center subsystems are Traffic Management, Transit Management, and Emergency Management.
Field - Intelligent infrastructure distributed along the transportation network which perform surveillance, information provision, and plan execution control functions and whose operation is governed by center subsystems. Field subsystems also directly interface to vehicle subsystems.
Travelers - Equipment used by travelers to access ITS services pre-trip and en-route. This includes services that are owned and operated by the traveler as well as services that are owned by transportation and information providers.
Vehicles - Covers ITS related elements on vehicle platforms. Vehicle subsystems include general driver information and safety systems applicable to all vehicle types. Three fleet vehicle subsystems (Transit, Emergency, and Commercial Vehicles) add ITS capabilities unique to these special vehicle types.
Terminators - Describe the boundary of the architecture. The interfaces between terminators and the subsystems and processes within the National ITS Architecture are defined, but no functional requirements are allocated to terminators.