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. See the Security Document for more information.

A document of the National Architecture that 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 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.

The service packages, formerly known as market packages, provide an accessible, service-oriented perspective to the National ITS Architecture. They are tailored to fit, separately or in combination, real world transportation problems and needs. Service packages collect together one or more equipment packages that must work together to deliver a given ITS service and the architecture flows that connect them and other important external systems. In other words, they identify the pieces of the physical architecture that are required to implement a particular ITS service. Service packages are implemented through projects (or groups of projects, aka programs) and in transportation planning, are directly related to ITS strategies used to meet regional goals and objectives.

A document of the National Architecture that expands upon the service package discussion in the Implementation Strategy document by providing a comprehensive review of each of the service packages describing how service packages can be used to plan and implement integrated transportation systems customized to local needs. This document includes a number of examples that illustrate ways service packages can be applied in regional ITS architecture and project ITS architecture development activities. Through these definitions, analyses, and examples, the Service Packages document provides a comprehensive review of the service packages and how they can be used to plan and implement integrated transportation systems customized to local needs.

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 or project 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.

A document of the National Architecture that 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.

A statewide prioritized listing/program of transportation projects covering a period of at least four years that is consistent with the long-range statewide transportation plan (LRSTP), metropolitan transportation plans (MTPs), and transportation improvement plans (TIPs), and is required for projects to be eligible for funding under title 23 U.S.C. and title 49 U.S.C. Chapter 53.

The official statewide multimodal, long-range transportation plan addressing no less than a 20-year planning horizon that is developed, adopted and updated by the state DOT through the statewide transportation planning process.

The principle structural element of the physical architecture 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 or project 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 or project ITS architecture, a Freeway Management System is a part of the overall surface transportation "system" for the region.

The list of all ITS-related elements in a regional ITS architecture or project ITS architecture.

Defined by International Council on Systems Engineering (INCOSE) as an interdisciplinary approach and means to enable the realization of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, and then proceeding with design synthesis and system validation while considering the complete problem. Systems engineering integrates all the disciplines and specialty groups into a team effort forming a structured development process that proceeds from concept to production to operation. Systems engineering considers both the business and the technical needs of all customers with the goal of providing a quality product that meets the user needs.

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 of the National ITS Architecture both contain the same set of terminators.

A document of the National Architecture that provides a detailed description of how the National ITS Architecture supports the services described by the Service 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 Service 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 (as shown in the diagram below). Microsoft Access databases are used to maintain these connections. The hyperlinked National ITS Architecture relies on this traceability to build the links that allows navigation between user services, logical architecture, and physical architecture.

Programs designed to reduce demand for transportation through various means, such as the use of public transit and of alternative work hours.

Legislated in 1998, TEA-21 authorized approximately $217 billion in federal funding for transportation investment for FYs 1998- 2003. Used for highway, transit, and other surface transportation programs. Superseded in 2005 by the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) legislation.

A prioritized listing/program of transportation projects covering a period of four years that is developed by an MPO as part of the metropolitan transportation planning process, consistent with the metropolitan transportation plan (MTP), and required for projects to be eligible for funding under title 23 U.S.C. and title 49 U.S.C. Chapter 53.

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.

An urbanized area with a population of 200,000 or more, as defined by the U.S. Bureau of the Census and designated by the Secretary of Transportation, or any additional area where TMA designation is requested by the Governor and the MPO and designated by the U.S. Secretary of Transportation.

See Long-Range Transportation Plan.

The process of examining travel and transportation issues and needs in an area. It includes a demographic analysis of the community in question, an examination of travel patterns and trends as well as an analysis of alternatives to meet projected future demands and for providing a transportation system that meets the community’s goals and objectives. Transportation planning is a cooperative process designed to foster involvement by all users of the system. Transportation planning process is required to be organized and directed for urbanized areas by a metropolitan planning organization (MPO) and for the state by the State Department of Transportation (DOT).

A measure of the amount of extra time (buffer) that travelers need to add to their average travel time to account for non-recurring delay. The buffer is the time between the average travel time and nearworst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time and is calculated as: Buffer Index (%) = (95th percentile travel time (in minutes) - average travel time (in minutes)) / average travel time (in minutes).

The ratio of the average travel time during the peak period, using congested speeds, to the off-peak period travel time, using posted or free-flow speeds.

Equipment used by travelers to access ITS services pre-trip and en-route. This includes equipment that are owned and operated by the traveler as well as equipment that are owned by transportation and information providers. The Traveler subsystems class is one of four general subsystem classes defined in the National ITS Architecture.

An automated software tool used to input and manage system inventory, service packages, architecture flows and interconnects of a regional ITS architecture and/or multiple project ITS architectures.

The principal direct federal funding agency for transportation facilities and programs in the United Stated. 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.

Miles traveled by all vehicles on a roadway.

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. The Vehicle subsystems class is one of four general subsystem classes defined in the National ITS Architecture.

A document of the National Architecture that is 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.

Ratio of the volume using a transportation facility to the capacity of that facility.

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.