National Transportation Communications for Intelligent Transportation System Protocol: Wikis


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The National Transportation Communications for Intelligent Transportation System Protocol (NTCIP) is a family of standards designed to achieve interoperability and interchangeability between computers and electronic traffic control equipment from different manufacturers.

The protocol is the product of a joint standardization project guided by the Joint Committee on the NTCIP, which is composed of six representatives each from the National Electrical Manufacturers Association (NEMA), the American Association of State Highway and Transportation Officials (AASHTO), and the Institute of Transportation Engineers (ITE). The Joint Committee has in turn formed 14 technical working groups to develop and maintain the standards, and has initiated or produced over 50 standards and information reports.[1]

The project receives funding under a contract with the United States Department of Transportation (USDOT) and is part of a wider effort to develop a comprehensive family of Intelligent Transportation System (ITS) standards.[2]


History of the NTCIP Development

NEMA initiated the development of the NTCIP in 1992. In early 1993, the US Federal Highway Administration (FHWA) brought together transportation industry representatives to discuss obstacles to installing field equipment for new Intelligent Transportation Systems (ITS). The representatives said that the number one priority was the need for an industry-wide standard data communications protocol. Since the NEMA Transportation Section members had already started work on a new industry standard, they offered to expedite and expand the scope of their activities.text.

The key objectives of the new NTCIP protocol were the interchangeability of similar roadside devices, and the interoperability of different types of devices on the same communications channel.

In 1996, the FHWA suggested a partnership of standards developing organizations to expand both user and industry involvement. AASHTO and ITE signed an agreement with NEMA to establish the Joint Committee on the NTCIP, and to work together on developing and maintaining the NTCIP standards.[1]

NTCIP Benefits

NTCIP standards offer increased flexibility and choices for agencies operating transportation management systems. NTCIP standards usage removes barriers to interagency coordination and allows equipment of different types and different manufacturers to be mixed on the same communications line. For these reasons, operating agencies benefit from specifying that NTCIP be included in all future acquisitions and upgrades, even if NTCIP is not initially used.[3]

According to the NTCIP Guide, use and application of the NTCIP provides the following benefits to Intelligent Transportation System (ITS) deployers:[3]

  • Avoiding Early Obsolescence — While retrofitting legacy equipment and systems with NTCIP support is not practical in most situations, most manufacturers offer NTCIP support in their ITS devices. It is possible to migrate a system gradually, since it is possible to operate a mixture of NTCIP and non-NTCIP devices in the same system, though not on the same communications line. Equipment may also continue to use a current protocol even though the device may also support NTCIP as a second protocol. Integrating legacy equipment and systems with NTCIP-conformant upgrades in this manner ensures that an operating agency’s systems and equipment remain useful and compatible long into the future.
  • Providing a Choice of Vendor — Since a computer system that supports NTCIP can communicate with any device from other vendors that are NTCIP-conformant, the number of vendors and systems, field devices, or software that can be considered for procurement increases greatly. While vendor-specific features may only be available to other software and ITS devices from the same vendor, the basic functionality described in an NTCIP standard is available regardless of vendor. This requires that agency specifications (procurement documents) adequately specify the mandatory and optional conformance requirements that support the agency’s functional requirements. However, NTCIP makes it easier for an agency to gradually change its software, controllers and other field devices from one vendor to supporting multiple vendors for the entire system.
  • Phased Procurement and Deployment — Specifying NTCIP allows agencies to procure devices and center systems in phases, over several financial cycles. For example, many agencies procure a few signs one year, then a few more the next year, and so on. Sometimes devices are procured from one vendor, and sometimes from multiple vendors. Specifying NTCIP standards means that multiple deployment phases, over multiple years, can be integrated, with little difficulty. The initial deployment establishes an ITS communications infrastructure that can be leveraged by future deployment phases resulting in improved cost/benefit for ITS projects.
  • Enabling Interagency Coordination — NTCIP allows agencies to exchange information and (with authorization) basic commands that enable any agency to monitor conditions in other agencies’ systems, and to implement coordinated responses to incidents and other changes in field conditions when needed. Such data exchange and coordinated response can be implemented either manually or automatically. One agency can monitor, and issue basic commands, if authorized, to field devices operated by another agency, even though those devices may be from a different vendor than those used by the monitoring agency. Potential applications of interagency coordination include:
    • (a) Coordinating timed transfers at a shared transit center,
    • (b) Coordinating traffic signals across jurisdictional boundaries,
    • (c) Providing traffic signal priority for selected, e.g., behind schedule, transit vehicles,
    • (d) Providing real-time information to a shared traveler information center,
    • (e) Monitoring traffic volumes on another agency’s roadway,
    • (f) Coordinating the operation of a freeway ramp meter with an adjacent traffic signal, or
    • (g) Posting a warning message on another agency’s dynamic message sign.
  • Use One Communications Network for All Purposes — NTCIP allows a management system to communicate with a mixture of device types on the same communications channel. For example, with the addition of appropriate application software in the system computer, a dynamic message sign could be installed near a signalized intersection, and the computer could communicate with the sign controller using the communications line or channel already in place for the traffic signal controller, if certain aspects of the communications protocols, that is, the Data Link and Physical layer protocols are the same. Similarly, a wide area network interface installed for communications with a system operated by another agency can be used for communications with any number of other systems, of any type, if NTCIP and the C2C Data Dictionaries and Message Sets of other efforts, such as the Traffic Management Data Dictionary (TMDD), are used. The communications network is usually one of the components of a transportation management system that requires the most resource investment. NTCIP ensures flexibility in the future use of that component.

NTCIP Communications Standards


Center to Field Device Communications

NTCIP has enabled the center to field communication and command/control of equipment from different manufacturers to be specified, procured, deployed, and tested. NTCIP communications standards for field devices are listed below: (the corresponding NTCIP document number is shown in parentheses):[3]

Center to Center Communications

Center to center (C2C) communication involves peer-to-peer communications between computers involved in information exchange in real-time transportation management in a many-to-many network. This type of communication is similar to the Internet, in that any center can request information from, or provide information to, any number of other centers.

An example of center to center communications is two traffic management centers that exchange real-time information about the inventory and status of traffic control devices. This allows each center system to know what timing plan, for example, the other center system is running to allow traffic signal coordination across center geographic boundaries. Other examples of this type of communication include:[3]

  • Two or more traffic signal systems exchanging information (including second-by-second status changes) to achieve coordinated operation of traffic signals managed by the different systems and to enable personnel at one center to monitor the status of signals operated from another center;
  • A transit system reporting schedule adherence exceptions to a transit customer information system and to a regional traveler information system, while also asking a traffic signal management system to instruct its signals to give priority to a behind-schedule transit vehicle;
  • An emergency management system reporting an incident to a freeway management system, to a traffic signal management system, to two transit management systems and to a traveler information system;
  • A freeway management system informing an emergency management system of a warning message just posted on a dynamic message sign on the freeway in response to its notification of an incident; and
  • A weather monitoring system (environmental sensors) informing a freeway management system of ice forming on the roadway so that the freeway management system is able to post warning messages on dynamic message signs as appropriate.

NTCIP communications standards for center to center communications are listed below: (the corresponding NTCIP document number is shown in parentheses):[3]

The NTCIP has coordinated with other information level standards development organizations during development of the center-to-center application profiles and supports the: ITE Traffic Management Data Dictionary (ITE TMDD), IEEE 1512 Incident Management (IEEE 1512), APTA Transit Communications Interface Profiles (APTA TCIP), and SAE J2354 Advanced Traveler Information Systems standards.

NTCIP Standards Framework

The NTCIP Framework is based primarily on the open standards of the Internet Engineering Task Force (IETF), World Wide Web Consortium (W3C), and ISO, plus NTCIP data dictionary standards specific for the task of ITS device communications. A layered, or modular, approach to communications standards, is used to represent data communications between two computers or other electronic devices.

NTCIP refers to “levels” in NTCIP, rather than “layers” to distinguish the hierarchical architecture applied from those defined by the Open System Interconnection Reference Model (OSI Model) of ISO and the Internet Engineering Task Force (IETF). The five NTCIP levels are: information level, application level, transport level, subnetwork level, and plant level.[3]

The figure below (used with permission) shows how the NTCIP Information, Application, Transport, Subnetwork, and Plant Levels.

NTCIP Framework. Reprinted from NTCIP 9001 v04 'The NTCIP Guide' by permission of NEMA.
NTCIP Framework.

To ensure a working system, deployers should select and specify at least one NTCIP protocol or profile at each level. A discussion of each level, and NTCIP standards that apply at that level, follows:[3]

  • NTCIP Information Level — Information standards define the meaning of data and messages and generally deal with ITS information (rather than information about the communications network). This is similar to defining a dictionary and phrase list within a language. These standards are above the traditional ISO seven-layer OSI model. Information level standards represent the functionality of the system to be implemented.
  • NTCIP Application Level — Application standards define the rules and procedures for exchanging information data. The rules may include definitions of proper grammar and syntax of a single statement, as well as the sequence of allowed statements. This is similar to combining words and phrases to form a sentence, or a complete thought, and defining the rules for greeting each other and exchanging information. These standards are roughly equivalent to the Session, Presentation and Application Layers of the OSI model.
  • NTCIP Transport Level — Transport standards define the rules and procedures for exchanging the Application data between point 'A' and point 'X' on a network, including any necessary routing, message disassembly/re-assembly and network management functions. This is similar to the rules and procedures used by the telephone company to connect two remotely located telephones. Transportation level standards are roughly equivalent to the Transport and Network Layers of the OSI model.
  • NTCIP Subnetwork Level — Subnetwork standards define the rules and procedures for exchanging data between two 'adjacent' devices over some communications media. This is equivalent to the rules used by the telephone company to exchange data over a cellular link versus the rules used to exchange data over a twisted pair copper wire. These standards are roughly equivalent to the Data Link and Physical Layers of the OSI model.
  • NTCIP Plant Level — The Plant Level is shown in the NTCIP Framework only as a means of providing a point of reference to those learning about NTCIP. The Plant Level includes the communications infrastructure over which NTCIP communications standards are to be used and has a direct impact on the selection of an appropriate Subnetwork Level for use over the selected communications infrastructure. The NTCIP standards do not prescribe any one media type over another. In most cases, communications media selections are made early in the design phase.

The NTCIP Framework does not preclude combinations beyond those expressly indicated on the diagram.


  1. ^ a b NEMA - NTCIP
  2. ^ US Department of Transportation ITS Standards Program
  3. ^ a b c d e f g The NTCIP Guide

External links


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