A framework within which a system can be built. Requirements dictate what functionality
the architecture must satisfy. An architecture functionally defines what the pieces of
the system are and the information that is exchanged between them. An architecture is
functionally oriented and not technology-specific which allows the architecture to remain
effective over time. It defines "what must be done", not "how it will be done'.
Information that is exchanged between subsystems and terminators in the physical
architecture view of the National ITS Architecture. Architecture flows are the primary
tool that is used to define the Regional ITS Architecture interfaces. These architecture
flows and their communication requirements define the interfaces which form the basis for
much of the ongoing standards work in the national ITS program. The terms "information flow"
and "architecture flow" are used interchangeably.
This is the basic building block of Regional ITS Architectures and Project ITS Architectures.
It is the name used by stakeholders to describe a system or piece of a system.
Equipment packages are the building blocks of the physical architecture subsystems. Equipment
Packages group similar processes of a particular subsystem together into an "implementable"
package. The grouping also takes into account the user services and the need to accommodate
various levels of functionality.
Information that is exchanged between subsystems and terminators in the physical architecture
view of the National ITS Architecture. These information flows are normally identical to the
architecture flows in the National ITS Architecture. The terms "information flow" and
"architecture flow" are used interchangeably.
Intelligent Transportation System
The system defined as the electronics, communications or information processing used singly
or integrated to improve the efficiency or safety of surface transportation.
See System Inventory.
Defines an architecture of interrelated systems that work together to deliver transportation
services. An ITS architecture defines how systems functionally operate and the
interconnection of information exchanges that must take place between these systems to
accomplish transportation services.
Any project that in whole or in part funds the acquisition of technologies or systems of
technologies that provide or significantly contribute to the provision of one or more ITS
The logical architecture view of the National ITS Architecture defines what has to be done
to support the ITS user services. It defines the processes that perform ITS functions and
the information or data flows that are shared between these processes.
The 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. Market packages collect together one or more equipment
packages that must work together to deliver a given transportation 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 transportation service.
National ITS Architecture
A common, established framework for developing integrated transportation systems. The
National ITS Architecture is comprised of the logical architecture and the physical
architecture, which satisfy a defined set of user service requirements. The National ITS
Architecture is maintained by the United States Department of Transportation (USDOT).
The physical architecture is the part of the National ITS Architecture that provides agencies
with a physical representation (though not a detailed design) of the important ITS interfaces
and major system components. It provides a high-level structure around the processes and data
flows defined in the logical architecture. The principal elements in the physical architecture
are the subsystems and architecture flows that connect these subsystems and terminators into
an overall structure. The physical architecture takes the processes identified in the logical
architecture and assigns them to subsystems. In addition, the data flows (also from the
logical architecture) are grouped together into architecture flows. These architecture flows
and their communication requirements define the interfaces required between subsystems, which
form the basis for much of the ongoing standards work in the ITS program.
Project ITS Architecture
A framework that identifies the institutional agreement and technical integration necessary
to interface a major ITS project with other ITS projects and systems.
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
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.
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
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.
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 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
The collection of all ITS-related elements in a Regional ITS Architecture.
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.
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.
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.