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Federal Highway Administration > Publications > Public Roads > Vol. 62· No. 2 > National ITS Architecture

Sept/Oct 1998
Vol. 62· No. 2

National ITS Architecture

by S. Lawrence Paulson

State and local transportation planners who want to make full use of the exciting potential of intelligent transportation systems (ITS) are learning that they don't have to go it alone.

The U.S. Department of Transportation (DOT) has launched a major effort to inform the transportation community about the National ITS Architecture, a framework designed to help ensure that ITS systems operate as efficiently as possible through integration and interconnection. The goal is to encourage the development of solutions that are good investments now and that will continue to pay dividends well into the future.

The National ITS Architecture was developed for DOT by a combined Lockheed Martin and Rockwell International team that used resources from the public and private sectors and from academia. It was completed in June 1996 after nearly three years of effort.

Simply described, the architecture is a master blueprint for the development of an integrated, multimodal intelligent transportation system. But unlike a blueprint for a home or factory, intended for use by a single set of builders, the National ITS Architecture is designed to be used by all transportation agencies that develop and operate federally funded ITS projects. The Transportation Equity Act for the 21st Century (TEA-21) requires such projects to be consistent with the architecture. (See TEA-21 article on page xx.)

Providing Coordination

ITS programs are in operation nearly everywhere in the country, providing proven benefits in such areas as traffic and transit management, toll collection, traffic-signal control, and traveler information. But these systems have been deployed on a project-by-project basis. Relatively little attention has been given to the issue of coordination across agency and jurisdictional boundaries.

When ITS systems can be designed to communicate and share information with other systems, everyone benefits. Such coordination increases efficiency, eliminates duplication, and saves time and money. It can also save lives and help the environment; studies have indicated that the benefits produced by an integrated transportation system include increased safety, decreased travel time, fewer delays, decreased fuel consumption, and reduced emissions. Although the list is certain to get longer as new technologies are developed, DOT has identified nine ITS infrastructure components that can currently be integrated to become a platform for managing travel in metropolitan areas:

  • Traffic control.
  • Freeway management.
  • Transit management.
  • Regional multimodal traveler information.
  • Emergency management.
  • Electronic fare payment.
  • Electronic toll collection.
  • Incident management.
  • Railroad grade crossing warning.

If those individual systems are pieces of a jigsaw puzzle, National ITS Architecture helps state and local transportation planners put the puzzle together in a way that begins to create real synergy. The resulting system goes far beyond being just the sum of its parts.

If the designer of a system at the traffic management center wants to send data to the transit management system, the architecture is a repository of the kinds of data that the designer might want to send, explains Mac Lister, travel management program coordinator for the ITS Joint Program Office at DOT. It can save a significant amount of design work and time. The architecture contains detailed specifications that can help the designer pick and choose what makes sense for any system design.

Lister points out that his office is already receiving testimonials about the benefits of the National ITS Architecture. The Colorado Department of Transportation, which is trying to integrate its infrastructure systems, developed a system specification in 60 days with three engineers using the architecture, saving an estimated six months of effort. The Southern California corridor network says the National ITS Architecture reduced by 50 percent the time it needed to define requirements for its new corridor system.

System architecture interconnection diagram. By planning for interfaces with other ITS components ahead of time, the risk of adding incompatible systems at a later date is reduced. The architecture allows for future extendibility and minimizes the need to replace the entire system to accommodate upgrades and additions.

But the National ITS Architecture is not a design document. It does not tell transportation planners what technology to select - only what functions to consider in making their own design decisions. It thus preserves planners' flexibility to respond to local needs and circumstances - for example, to choose fiber-optic over twisted-pair technology for wireline communications. The architecture is a starting point for making decisions about how to meet specific local and regional needs through the implementation and coordination of ITS.

Creating a Common Vocabulary

Now that the National ITS Architecture has been completed, work is underway to write the standards that will help create a common vocabulary to enable ITS elements to understand each other.

Lister explains the distinction between the architecture and the standards in this way: The architecture talks about the kinds of data that might flow between a transit management center and a traffic management center, whereas the standards are actually detailed hardware or software interfaces. The architecture is a much higher level representation of the information, while the standards tell which wires must connect to which other wires and the specific message set that occurs between various pieces of the infrastructure.

With an architecture and no standards, systems could have similar designs and function in similar ways but might be incapable of exchanging information seamlessly. Transportation planners might be forced to choose either off-the-shelf traffic control software that cannot be easily upgraded and might not fully meet the system's needs or expensive custom-designed programs that work only with a particular combination of equipment.

The ITS standards development process calls for the use of open, nonproprietary standards that will encourage multiple vendors to enter the market, giving transportation agencies a choice of suppliers for equipment, support, and upgrades. Competition will hold down prices and encourage innovation.

The ITS standards are being developed cooperatively by public and private sector experts working through existing standards-developing organizations (SDOs). The following SDOs are currently involved in this effort: the American Association of State Highway and Transportation Officials (AASHTO), the Institute of Transportation Engineers (ITE), the American Society for Testing and Materials (ASTM), the National Electrical Manufacturers Association (NEMA), the American National Standards Institute (ANSI), the Society of Automotive Engineers (SAE), and the Institute of Electrical and Electronics Engineers (IEEE).

Standards development is designed to be an extremely democratic process, open to any interested party. Proposed standards will be available for public comment, and balloting procedures are aimed at ensuring that final versions of standards have widespread support before they are adopted. A testing period will follow the adoption of a standard, giving further assurance that the resulting technology will meet the goals of the National ITS Architecture. It is expected that more than 20 ITS standards will be adopted by the end of this year.

Reaching Out to the Regions

An extensive outreach program on the National ITS Architecture is being conducted by the Federal Highway Administration (FHWA) and other agencies of DOT. The program, which began this spring with a series of 10 meetings throughout the country, is designed to acquaint transportation planning and other agencies with the ITS architecture and the way that DOT sees the concept being implemented by its state and local transportation partners.

The meetings also give DOT facilitators an opportunity to impart several key messages about the effort to ensure consistency with the National ITS Architecture. One message is that the policy regarding consistency is still under development and is subject to modification as a result of discussions with DOT's state and local transportation partners. In addition, the requirements will be phased-in over time. DOT expects that it will be several years before the full policy goes into effect. Another key message is that DOT won't require the replacement of existing ITS systems or equipment that have proprietary interfaces. Instead, DOT will encourage transportation partners to make future investments with the objectives of the national architecture in mind to facilitate the electronic sharing of data.

As DOT facilitators lead participants in the outreach sessions through an outline of the National ITS Architecture planning process as it is currently envisioned, they stress that it will be a purely local decision to determine which agency will take the lead in developing a regional ITS architecture.

"What we're saying is that whoever in the area wants to push the technology, the development of the ITS infrastructure - it could be the state department of transportation; it could be the local transit agency - that entity would be the champion of developing this regional architecture. Ultimately, it needs to get incorporated into the transportation plan that the metropolitan planning organization [MPO] adopts. But that doesn't mean the MPO has to develop it," Lister explained.

Regardless of who takes the lead, DOT facilitators have been telling participants in regional outreach sessions that it's important to involve as many transportation agencies and organizations as possible in the process of developing a regional ITS architecture. This may include groups not traditionally involved in the planning process, such as emergency services, bureaus of travel and tourism, incident management, and information service providers.

After the group is formed, the next steps are to identify how local and regional needs can be met by ITS, what ITS components are currently in place, and what components need to be acquired in the future. The final step is to define a regional architecture. This is basically a high-level design for regional ITS that relates the ITS components that a region already has and the components it wants to have to the National ITS Architecture.

Once these steps have been completed, DOT's implementation plan envisions that regions will take these follow-up steps:

  • Decide on a concept of operations. A region should identify its vision of using ITS, decide who is going to do what, and describe how it will operate.
  • Decide on the roles and responsibilities of stakeholders. Consider linkages with capital improvement projects. Regions may want to explore where ITS components can be included in planned projects, such as facility reconstruction, new bus purchases, or capacity expansion.
  • Consider how implementation can be phased-in. Based on available resources, regions should decide where the architecture can be implemented first and which services will be targeted.
  • Determine whether regional technology agreements will be needed. A decision to implement toll technology, for example, may require that an agreement be reached with everyone involved on the use of a common technology.

Clarifying the Federal Role

In general, the federal role in ensuring consistency with the National ITS Architecture will be same as the existing federal role in the transportation planning process and in federal-aid projects.

At the project level, FHWA's roll depends on the system designation and agreements with the contracting agency. For projects not requiring federal oversight, the contracting agency is responsible for ensuring consistency with the National ITS Architecture much in the same way that they ensure compliance with other federal requirements. For projects with federal oversight, FHWA will work with the contracting agency to ensure consistency.

ITS experts at DOT emphasize that being consistent with the National ITS Architecture is not a regulatory program but an effort to encourage the adoption of planning practices that will take full advantage of available technology and promote the seamless exchange of information. As emphasized in a brochure for senior transportation managers, the architecture does not dictate the design of your system, but rather it helps to align the requirements for the deployment envisioned.

Lister promises that DOT will try to keep documentation requirements to a minimum.

National ITS Architecture will tie together ITS programs.National ITS Architecture will tie together ITS programs. Nevertheless, DOT is planning to provide plenty of guidance on how to achieve consistency with the National ITS Architecture. Federal assistance is expected to include a three-day training course on how to implement regional systems using the National ITS Architecture; a sample ITS planning document showing the level of detail that may be appropriate; National ITS Architecture documents, databases, and other tools available on a single CD-ROM at no charge; and technical assistance documents for those involved in the planning, development, deployment, and operation of particular systems, including transit, traffic-signal control, freeway and incident management, and traveler information.

As Lee Simmons wrote in a previous article for Public Roads, "The architecture is the framework that makes possible a national infrastructure of integrated, intermodal, and interoperable ITS. As such, its development is the cornerstone achievement of the national ITS program."

S. Lawrence Paulson is a partner in Hoffman Paulson Associates, a writing/editing and public relations firm in Hyattsville, Md. He has written and edited numerous studies for the Federal Highway Administration, Federal Transit Administration, and National Highway Traffic Safety Administration. He also spent seven years covering Congress as the Washington bureau chief of a national daily newspaper, The Oil Daily.

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