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About ITS Standards
Glossary
Application Area
Application areas refer to components of ITS systems from the deployer’s perspective. The standards which apply to each of those components can be determined from the application area matrix. For example, one application area is Dynamic Message Signs (LED-based roadway signs that can be programmed to display any message). A state DOT manager who wanted to install a set of such signs could look up the Dynamic Message Sign application area in the application area matrix. He or she would then see that standards relevant to most Dynamic Message Sign deployments include NTCIP standards 1101, 1102, 1103, 1201, 1203, 2101, 2102, 2103, 2104, 2201, 2202, 2301, and 2303. This list offers a starting point for determining which standards are of interest in this DOT manager’s particular project.
Architecture Flow
Information that is exchanged between physical objects, either subsystems and terminators, in the physical view of the National ITS Reference Architecture, also known as ARC-IT. 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.
Center Subsystems
ARC-IT Physical Objects or Subsystems that provide management, administrative, and support functions for the transportation system. The center subsystems each communicate with other centers to enable coordination between modes and across jurisdictions. Some examples of center subsystems are Traffic Management, Transit Management, Commercial Vehicle Administration, Archived Data Management, Emissions Management, Payment Administration, Emergency Management, Transportation Information Center, and Fleet and Freight Management. One of five general physical object classes defined in ARC-IT.
Communications Layers or Levels
As defined within the NTCIP project, these refer to five layers of technology upon which ITS systems are built. The underlying layer is the physical connection layer; intermediate layers include subnetwork type, transport protocol, and communication application choice; and the highest layer is the contents of the message that is sent. Different types of standards apply to different layers.
Data Flows
Data flows are unaggregated types of communication which flow between functions within the ARC-IT. They are aggregated into information flows, which are the subject of standardization efforts.
Dedicated Short Range Communications
A wireless communications channel used for close-proximity communications between vehicles and the immediate infrastructure. It supports location-specific communications for ITS capabilities such as toll collection, transit vehicle management, driver information, and automated commercial vehicle operations. One of the types of architecture interconnects defined in ARC-IT.
Deployment/Deployer
Deployment is used to describe the process of implementing an standard in a real-world project. "Deployer" refers to the organization (or particular staff member) that manages the implementation.
Development Status
The term "development status" refers to formal classification of the extent to which a standard in development has been reviewed and revised. Although precise criteria for promotion from one development status to the next vary slightly from SDO to SDO, the consensus-based standards development process means that the standard is continuously examined and improved before it is deemed ready to be published.
Field Subsystems
ARC-IT Physical Objects comprised of intelligent infrastructure distributed along the transportation network which perform surveillance, information provision, and plan execution control functions and whose operation is governed by center subsystems. Field subsystems also directly interface to vehicle subsystems. One of the five general physical object classes defined in ARC-IT.
Fixed-Point to Fixed-Point Communications
Communication links serving stationary entities. It may be implemented using a variety of public or private communication networks and technologies. It can include, but is not limited to, twisted pair, coaxial cable, fiber optic, microwave relay networks, spread spectrum, etc. In Fixed-Point to Fixed-Point (FP2FP) communication the important issue is that it serves stationary entities. Both dedicated and shared communication resources may be used. This includes interconnects defined in ARC-IT as Center-to-Center, Field-to-Field, or Center-to-Field.
Functional Requirement
A statement that specifies WHAT a system must do. The statement should use formal "shall" language and specify a function in terms that the stakeholders, particularly the system implementers, will understand. In the ARC-IT, Functional Requirements have been defined for each Functional Object that focus on the high-level requirements that support regional integration.
Functional View
The functional view of ARC-IT defines what has to be done to support the ITS services. It defines the processes that perform ITS functions and the information or data flows that are shared between these processes. The functional view was developed using Structured Analysis techniques and consists of a heirarchical set of process specifications and data dictionary entries. The functional view is not technology specific, nor does it dictate a particular implementation. This implementation independence makes the functional view accommodating to innovation, scalable from small scale implementations to large regional systems, and supportive of widely varied system designs.
Information Flow
Information that is exchanged between physical objects, either subsystems and terminators, in the physical view of ARC-IT. Information flows are the primary tool that is used to define the Regional ITS Architecture interfaces. These information 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.
Interconnects
In order for physical objects to communicate with each other, one or more of the telecommunication connections would be used to make a link between the physical objects. For example, the communication between a "center" subsystem and another "center" subsystem (such as a traffic management center communication with a transit management center) belongs to the center-to-center (C2C) interconnect. Other communications interconnects include center-to-field (C2F), wide area wireless (mobile), field-to-field, field-to-vehicle also known as vehicle to infrastructure or V2I, and vehicle-to-vehicle (V2V).
Examples of ITS applications that belong to different interface classes can be found under the application area section of the website. Applications of the same interface class will have similar requirements, specifications, and standards. For example, by looking at the physical view diagram, one can conclude that all C2C ITS systems require a wireline connection be in place. Indeed, all C2C applications share a common set of 11 communications protocol standards. Similarly, all C2F applications share a common set of 12 communication protocol standards.
The actual data that flow on these communication links are the data flows depicted in the functional view. The details of the protocols and standards required for the communications to take place are depicted in ARC-IT’s communications view.
To learn more about communication interfaces, consult the ARC-IT Comm View.
Interoperability
ITS America's Interoperability Subcommittee adopted the following, in accord with ISO TC 204, as the definition of interoperability: "Interoperability is the ability of systems to provide services and to accept services from other systems and to use the services so exchanged to enable them to operated effectively together." In examining systems for interoperability, it is useful to distinguish two degrees of interoperability, "pair-wise," and "end-to-end" interoperability. Pair-wise interoperability involves verifying that two systems are able to exchange data and that the data has the same meaning to each system and leads to the expected functionality. "End-to-end" interoperability involves verifying that the flow and use of data are consistent from initial input to final outcome.
ITS
The integrated application of advanced computer, electronics, and communications technologies to increase the safety and efficiency of surface transportation is known as Intelligent Transportation Systems (ITS). ITS offers a complement or an alternative to traditional engineering methods for increasing throughput, safety, etc. It makes possible increasing throughput without paying for road-widening, attracting more transit passengers without buying more buses, or reducing fuel consumption without redesigning vehicles.
ITS Architecture
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. 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."
National ITS Reference Architecture
The National ITS Reference Architecture, also known as the Architecture Reference for Cooperative and Intelligent Transportation, provides a framework for planning, defining, and integrating intelligent transportation systems. It reflects the contributions of a broad cross-section of the ITS community (transportation practitioners, systems engineers, system developers, technology specialists, consultants, etc.). The Architecture represents a national consensus on the course that ITS development should take in the United States.
Physical View
The physical view is the part of the National ITS Referece Architecture (or "ARC-IT") 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 functional view. The principal elements in the physical view are the physical objects, including subsystems that have functionality and terminators or external systems for which functionality is not defined, along with information flows that connect these physical objects into an overall structure.. The physical view takes the processes identified in the functional view and assigns them to subsystems. In addition, the data flows (also from the functional view) are grouped together into information flows. These information flows and their communication requirements define the interfaces required between physical objects, which form the basis for much of the ongoing standards work in the ITS program.
Project ITS Architecture
High-level design specifications based on national and regional standards and regional ITS needs.
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.
Service Package
The service packages provide an accessible, service-oriented perspective to ARC-IT. They are tailored to fit, separately or in combination, real world transportation problems and needs. Service packages collect together one or more physical objects and their functional objects that must work together to deliver a given transportation service and the information flows that connect them and other important external systems. In other words, they identify the pieces of the physical view that are required to implement a particular transportation service.
Standards
Standards specify how to do things consistently. They may specify how things should work, or they may describe certain physical attributes. Some everyday examples where standards are important are the keyboard you are typing on (imagine if every keyboard had different key positions) and the outlet your computer is plugged into (imagine if electrical outlets and voltages were all different). These are just a few things that use standards to help make our lives less complicated. Generally, standards are used to:
- Speed acceptance and deployment of products and services
- Enable compatibility, interchangeability, and/or interoperability
- Contain costs
- Minimize confusion
- Assure quality
Standards Development Organization
A standards development organization (SDO) is an organization, usually a private non-profit professional or industry organization, which manages the development of open, non-proprietary standards. Each SDO has its own strict protocol which governs the process by which drafts are created and revised with maximum input from experts in the field, so that the final product is robust, represents the best practices in the industry, and is acceptable to different types of stakeholders. In the U.S., SDOs are often accredited by the American National Standards Institute (ANSI).
Standards Development Process
Refers to the consensus-based protocol by which standards development organization develop open, non-proprietary standards. This process consists of convening a working group, consisting of professionals with domain expertise in the specific ITS component to which the standard is expected to apply. Their duty is to shepherd the standard draft through a series of development statuses. Promotion to each successive development status means that the draft has been reviewed by an ever-widening group of stakeholders. Thus, the standard is continuously examined and improved before it is deemed ready to be published. Revised versions may be released after this.
Subsystem
Subsystems are physical objects that correspond to the actual equipment, both hardware and software, that physically carry out the ITS functions. They are the principal structural elements of the physical view (which you can view by clicking on the Physical View button at https://www.arc-it.net). Subsystems provide a physical representation (though not a detailed design) of important ITS interfaces and major system components. There are 40 subsystems in ARC-IT. These are grouped into five classes: Centers, Field, Vehicles, Support, and Travelers. Example subsystems include the Traffic Management Center, the Vehicle Onboard Equipment (OBE), and the ITS Roadway Equipment Subsystem. Due to this close correspondence between the physical world and the subsystems, the subsystem interfaces are prime candidates for standardization.
Systems Engineering
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.
Terminator
Terminators are the physical objects that define the boundary of an architecture. In ARC-IT terminators represent the people, systems, and general environment that interface to ITS. The interfaces between terminators and the subsystems and processes within ARC-IT are defined, but no functional requirements are allocated to terminators. The functional and physical views of ARC-IT have exactly the same set of terminators. The only difference is that functional view processes communicate with terminators using data flows, while physical view subsystems use information flows.
Traveler Subsystems
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 five general subsystem classes defined ARC-IT.
USDOT ITS JPO
The U.S. Department of Transportation's ITS Joint Program Office was created in 1994 to streamline ITS development and deployment initiatives beginning in various DOT agencies. In recognition of the interdisciplinary nature of ITS, the JPO was established to: (1) provide strategic leadership for ITS research, development, testing, and deployment, (2) guide policy coordination, and (3) ensure resource accountability. Responsibility for the actual implementation of ITS activities rests with individual program and modal administrations. These include the Federal Highway Administration (FHWA), Federal Transit Administration (FTA), the National Highway Traffic Safety Administration (NHTSA), the Federal Railroad Administration (FRA), the Federal Motor Carrier Safety Administration (FMCSA), and the Maritime Administration (MARAD).
USDOT ITS Standards Program
The USDOT's ITS Standards Program is a consensus-building effort to promote the widespread deployment of interoperable ITS systems by supporting the participation of stakeholders and accelerating the development and deployment of ITS standards. The major program elements are Standards Development, Standards Testing, Outreach and Education, Technical Assistance, and Policy Support.
Vehicle Subsystems
Covers ITS related elements on vehicle platforms. Vehicle subsystems include general driver information and safety systems applicable to all vehicle types. Five fleet vehicle subsystems (Transit, Emergency, Commercial, Freight Equipment, and Maintenance and Construction Vehicles) add ITS capabilities unique to these special vehicle types. One of five general subsystem classes defined in ARC-IT.
Vehicle to Vehicle Communications
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 ARC-ITF.
Wide Area Wireless Communications
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.
Working Group
Working groups consist of professionals with domain expertise in the specific ITS component to which the standard is expected to apply. They are usually a mix of SDO staff, technical consultants, and public sector (usually state-level) transportation agency representatives. A working group is selected and convened, under the direction of the sponsoring SDO, for each standard after a proposal for its development has been accepted.