Real-Time Updates

Changes to data reflected in a short enough period of time such that the data appears to reflect reality at the moment the data is examined.

Record of Decision

A record of agreement that a proposed project meets all applicable requirements of the National Environmental Policy Act (NEPA), as issued by the designated lead agency.

Reference Architecture

An architecture that is used to guide the production of other architectures. Note: In this context the word 'architecture' refers to the term 'architecture description' from the ISO/IEC/IEEE 42010 model of a system architecture.


The geographical area that identifies the boundaries of the regional ITS architecture and is defined by and based on the needs of the participating agencies and other stakeholders. In metropolitan areas, a region should be no less than the boundaries of the metropolitan planning area.

Regional Activity Center

A major facility or area at which an interregional, interstate or international trip begins or ends. Regional activity centers should be connected to the Strategic Intermodal System via regional and local strategic linkages. Examples include central business districts, theme parks or freight distribution centers.

Regional ITS Architecture

A specific, tailored framework for ensuring institutional agreement and technical integration for the implementation of ITS projects or groups of projects in a particular region. It functionally defines what pieces of the system are linked to others and what information is exchanged between them.

Regional Planning Council (RPC)

An organization that promotes communication, coordination and collaboration among local governments, metropolitan planning organizations and other local regional authorities on a broad range of regional issues, including transportation and land use planning.

Regionally Significant Facility

A facility that connects urban, urbanizing or rural areas within multi-county regions, provides connections from regional activity centers to the Strategic Intermodal System (SIS)/Emerging SIS, or otherwise serves important regional travel. Examples of regionally significant facilities could include highway, waterway, rail and transit corridors serving major regional commercial, industrial or medical facilities; and regional transportation hubs such as passenger terminals, commercial service and major general aviation airports, deep-water and special generator seaports, and major regional freight terminals and distribution centers.


A repository for maintaining data requester's information including the type of data they are subscribing to, their address, etc.


Providing consistent and dependable system output or results.

Remote Vehicle

A connected vehicle that periodically and dynamically broadcasts a message about its general situation to a host vehicle. (See Host Vehicle).

Repackage Data

Data that is broken down for aggregation, parsing or sampling. A function within a data distribution system.

Request for Quotation (RFQ)

A request for services, research, or a product prepared by a customer and delivered to a contractor with the expectation that the contractor will respond with their proposed cost, schedule, and development approach.


Statement which translates or expresses a need and its associated constraints and conditions (see ISO/IEC/IEEE 15288). A well-formed specified requirement contains one or more of the following:
- has to be met or possessed by a system to solve a problem, achieve an objective, or address a stakeholder concern
- is qualified by measurable conditions and bounded by constraints
- defines the performance of the system when used by a specific stakeholder or the corresponding capability of the system, but not a capability of the user, operator, or other stakeholder; and
- can be verified (e.g., the requirements realization can be proven to the customer's satisfaction at the level the requirement exists).
Requirements at lower levels align with the design of the higher level physical system. For more details on what makes a good requirement, what makes a complete set of requirements and how to perform requirements engineering, see ISO/IEC/IEEE 29148.


In the enterprise view of ARC-IT, a resource is anything available to a system that can support the achievement of objectives; i.e., any physical or virtual element that may be of limited availability within a system. In this context a Resource has some role, offers services, and performs some action within a system. A resource may serve more than one activity.

Resurfacing Program

Provides for pavement resurfacing, rehabilitation, minor reconstruction, and pavement milling and recycling. Such projects are intended to preserve the structural integrity of highway pavements.


The publication by a relevant authority of the information that a particular certificate is no longer to be trusted.

Right of Way

The right of one vehicle or pedestrian to proceed in a lawful manner in preference to another vehicle or pedestrian.

Risk Analysis

A legacy document of the National Architecture that presented an analysis of potential critical risks that may delay or prevent the deployment of ITS technologies, and recommends mitigation plans which will eliminate or reduce these risks to the deployment process. It was intended for implementers that are involved with the details of ITS deployment in their region, throughout the development of the regional ITS architecture.

Road Weather Information System (RWIS)

A combination of technologies that collects, transmits, models, and disseminates weather and road condition information.

Roadside unit

A fixed-position cooperative device. This may be a permanent installation or temporary equipment brought on-site for a period of time associated with an incident, road construction, or other event.


The way in which an object participates in a relationship; an object's set of behaviors and actions associated with the relationship of that object with other objects.

Root Certificate

A self-signed certificate that can be used as a trust anchor to verify other certificates.

Rumble Strip

A textured or grooved pavement sometimes used on or along shoulders of highways to alert motorists who stray onto the shoulder.


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