A term used in transit operations to describe an operator work assignment.

Scalable Vector Graphics (SVG) is a language for describing two-dimensional graphics and graphical applications that is backed by the World Wide Web Consortium. Graphics described in SVG file format can be scaled without losing graphic quality. SVG files can be compressed to accommodate faster downloads of the graphic. The National ITS Architecture uses compressed SVG format to view the data flow diagrams (DFDs) from the logical architecture. The first time you open one of these diagrams you may be prompted to download an SVG Viewer as an add-on to your existing Web Browser.

The protection of ITS itself is comprised of security services that protect ITS systems and the communications between them.

The Security Document presents an overview of the topic of security in the National ITS Architecture. It provides the context and considerations for using the security-related parts of the National ITS Architecture. This document also provides high-level guidance to agencies that desire to include security considerations in their regional ITS architectures and project ITS architectures. In addition to defining eight functional security areas as part of the National ITS Architecture, this document also discusses securing ITS itself.

Providing security for the surface transportation system has a set of desired outcomes (or objectives). How well a security system performs can be measured by the extent to which it provides meets the desired objectives.

Security services are typical security mechanisms or countermeasures that provide for different aspects of security.

Security threats are events or circumstances that adversely impact a surface transportation system or communication between systems.

A widely used term that notates a public agency, private organization or the traveling public with a vested interest, or a "stake" in one or more transportation elements within a Regional ITS Architecture.

Documented technical specifications sponsored by a Standards Development Organization (SDO) to be used consistently as rules, guidelines, or definitions of characteristics for the interchange of data. A broad array of ITS standards is currently under development that will specifically define the interfaces identified in the National ITS Architecture.

This document discusses the issues that are involved in the development of system interface standards. It was primarily intended as a planning document for US DOT and the Standards Development Organizations.

This document is the official statewide intermodal transportation plan that is developed through the statewide transportation planning process.

The principle structural element of the physical architecture view of the National ITS Architecture. Subsystems are individual pieces of the Intelligent Transportation System defined by the National ITS Architecture. Subsystems are grouped into four classes: Centers, Field, Vehicles, and Travelers. Example subsystems are the Traffic Management Subsystem, the Vehicle Subsystem, and the Roadway Subsystem. These correspond to the physical world: respectively traffic operations centers, automobiles, and roadside signal controllers. Due to this close correspondence between the physical world and the subsystems, the subsystem interfaces are prime candidates for standardization.

A diagram which depicts all subsystems in the National ITS Architecture and the basic communication channels between these subsystems. The subsystem diagram is a top-level architecture interconnect diagram. Variations of the subsystem diagram are sometimes used to depict Regional ITS Architectures at a high level.

A collection of hardware, software, data, processes, and people that work together to achieve a common goal. Note the scope of a "system" depends on one's viewpoint. To a sign manufacturer, a dynamic message sign is a "system". To a state DOT, the same sign is only a component of a larger Freeway Management "System". In a Regional ITS Architecture, a Freeway Management System is a part of the overall surface transportation "system" for the region.

The collection of all ITS-related elements in a Regional ITS Architecture.

A structured process for arriving at a final design of a system. The final design is selected from a number of alternatives that would accomplish the same objectives and considers the total life-cycle of the project including not only the technical merits of potential solutions but also the costs and relative value of alternatives.

Terminators define the boundary of an architecture. The National ITS Architecture terminators represent the people, systems, and general environment that interface to ITS. The interfaces between terminators and the subsystems and processes within the National ITS Architecture are defined, but no functional requirements are allocated to terminators. The logical architecture and physical architecture views of the National ITS Architecture both have exactly the same set of terminators. The only difference is that logical architecture processes communicate with terminators using data flows, while physical architecture subsystems use architecture flows.

This document provides a detailed description of how the National ITS Architecture supports the services described by the Market Packages. Transaction set diagrams and accompanying narrative are used to provide the detailed description. These transaction set diagrams provide sequential dependencies among the information flows in each Market Package. It is a technical document, intended for engineers, operators, and others involved in the development of regional ITS architectures or project ITS architectures.

A cornerstone of the National ITS Architecture is the traceability between its components. Microsoft Access databases are used to maintain these connections. The hyperlinked National ITS Architecture relies on this traceability to build the links that allows traversal between user services, logical architecture, and physical architecture.

One of three layers (along with the communications layer and the institutional layer) defined by the physical architecture. The transportation layer shows the relationships among the transportation related elements. It is composed of subsystems for travelers, vehicles, transportation management centers, and field devices, as well as external system interfaces (terminators) at the boundaries.

Also called the "Long Range Transportation Plan", this plan defines the state or metropolitan area's long-term approach to constructing, operating, and maintaining the multi-modal transportation system.

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. One of four general subsystem classes defined in the National ITS Architecture.

An automated software tool used to input and manage system inventory, market packages, architecture flows and interconnects with regard to a Regional ITS Architecture and/or multiple Project ITS Architectures.

The principal direct federal funding agency for transportation facilities and programs. The United States Department of Transportation (USDOT) includes the Research and Innovative Technology Administration (RITA), the Federal Highway Administration (FHWA), the Federal Transit Administration (FTA), the Federal Railroad Administration (FRA), and others.

A specific functional requirement statement of what must be done to support the ITS user services. The user service requirements were developed specifically to serve as a requirements baseline to drive National ITS Architecture development. The user service requirements are not to be construed as mandates to system/architecture implementers, but rather are directions to the National Architecture Team. As a requirements baseline, the user service requirements include little narrative or background material. For a general introduction to the user services, consult the National Program Plan.

User services document what ITS should do from the user's perspective. A broad range of users are considered, including the traveling public as well as many different types of system operators. User services, including the corresponding user service requirements, form the basis for the National ITS Architecture development effort. The initial user services were jointly defined by USDOT and ITS America with significant stakeholder input and documented in the National Program Plan. The concept of user services allows system or project definition to begin by establishing the high level services that will be provided to address identified problems and needs. New or updated user services have been and will continue to be satisfied by the National ITS Architecture over time.

A logical grouping of user services that provides a convenient way to discuss the range of requirements in a broad stakeholder area. In the National Program Plan's user service requirements, the user services are grouped into eight bundles: Travel and Traffic Management, Public Transportation Management, Electronic Payment, Commercial Vehicle Operations, Emergency Management, Advanced Vehicle Safety Systems, Information Management, and Maintenance and Construction Operations.

Dedicated wireless system handling high data rate, low probability of error, line of sight communications between vehicles. Advanced vehicle services may use this link in the future to support advanced collision avoidance implementations, road condition information sharing, and active coordination to advanced control systems. One of the types of architecture interconnects defined in the National ITS Architecture.

Covers ITS related elements on vehicle platforms. Vehicle subsystems include general driver information and safety systems applicable to all vehicle types. Four fleet vehicle subsystems (Transit, Emergency, Commercial and Maintenance and Construction Vehicles) add ITS capabilities unique to these special vehicle types. One of four general subsystem classes defined in the National ITS Architecture.

Written in "magazine style", the Vision Statement sketches a number of possible scenarios of ITS development over the next 20 years. It describes how travelers and system operators may be able to use and benefit from ITS technologies in their day.

A communications link that provides communications via a wireless device between a user and an infrastructure-based system. Both broadcast (one-way) and interactive (two-way) communications services are grouped into wide-area wireless communications in the National ITS Architecture. These links support a range of services in the National ITS Architecture including real-time traveler information and various forms of fleet communications. One of the types of architecture interconnects defined in the National ITS Architecture.

Windows Metafile. A graphics file format, originated by Microsoft Corporation. Images in WMF format can be resized without distortion and loss of detail. Available for download for selected diagrams (e.g., architecture flow diagrams). Many diagrams displayed on the National ITS Architecture CD-ROM and web site are actually in GIF format.