The sending of a message to a single network destination identified by a unique address.

United States Department of Transportation (USDOT)

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.

Upper Layers

The ITS Application Entity and Facilities Layer of the ARC-IT communications reference model, along with any related functionality of the Management and Security Entities.


An entity or individual who uses a computer, program, network, and related services of a hardware and/or software system, usually associated with granting that individual with an account and permissions.
In the case of ARC-IT this includes System Users that refers to the combination of Mobile, Field, and Center based devices and applications. The term End User refers to the human user of the System User device. End Users may not interact directly with all of the internal or core transportation systems, but are referred to as the ultimate beneficiaries or participants in the ITS environment.

User Need

A capability that is identified to accomplish a specific goal or solve a problem that is to be supported by the system.

User Service Requirement

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

User services documented what ITS should do from the user's perspective. A broad range of users were considered, including the traveling public as well as many different types of system operators. User services, including the corresponding user service requirements, formed the basis for the original 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.

User Services Bundle

A logical grouping of user services from the original National ITS Program Plan that provided a convenient way to discuss the range of requirements in a broad stakeholder area. In the National Program Plan, the user services were 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.