The IVHS architecture program: a systematic approach to progress

Public Roads, Summer, 1994

This article is adapted from materials provided by the Federal Highway Administration's (FHWA) IVHS Program Management and Systems Engineering Division and from an article in the January 1994 IVHS Architecture Bulletin, published by IVHS AMERICA.

Introduction: Why a System Architecture?

The Intelligent Vehicle-Highway System (IVHS) is a large umbrella program that consists of a number of different user services in the categories of travel and traffic management, public transportation management, electronic payment, commercial vehicle operations, emergency management, and advanced vehicle safety systems. These services are related in that they all involve collecting, transmitting, processing, distributing, and displaying information. Moreover, the same information may be common to different user services and system components may be designed to accommodate requirements for multiple services.

The complexity and enormity of IVHS, its numerous and byzantine interconnections, and its far-reaching applications and implications all demand that it be put together from the start in a well-thought-out manner. This up-front planning will ensure that the deployment of IVHS user services will occur within the most sensible system framework. It will also ensure that a nationally compatible system emerges, instead of having local or regional pockets of IVHS that will not accommodate intercity travel or cross-country goods movement. For all of these reasons, IVHS needs a system architecture. In addition, Section 6053 (b) of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) requires the Secretary of Transportation to develop and implement standards and protocols that "... shall promote compatibility among intelligent vehicle-highway systems tecnologies implemented throughout the States."

What Is a System Architecture?

A system architecture is the framework that describes how system components interact and work together to achieve total system goals and objectives. It describes the total system's operation, what each component of the system does, and what information is exchanged among the components. An architecture is neither hardware nor software. Rather, it is described on paper as charts and narrative--like a flowchart for a computer program.

The IVHS system architecture should be an open one. An open architecture allows for flexibility and innovation. It is functional so that hardware and software products from multiple vendors can be provided to meet system needs, thereby facilitating competition. It is modular to permit and facilitate the introduction of new technologies and system capabilities over time.

How Is a System Architecture Developed?

The development of an architecture is typically a top-down, systematic process. It involves an understanding of system goals and objectives, the functions and functional requirements a system has to meet to achieve these goals and objectives, and the different operational concepts and enabling technologies that can be used to build a system that satisfies the functional requirements. Furthermore, the system development involves rigorous analysis of the costs and impacts of different architectural approaches and broad consideration of the feasibility of implementing the system. The process also involves iteration, even to the point of evolving system goals and objectives and functions and functional requirements.

How Is the IVHS Architecture Being Developed?

ISTEA requires the Department of Transportation (DOT) to provide the leadership and guidance necessary to ensure national IVHS compatibility over the long term. That compatibility relies upon establishing a unifying national IVHS architecture. It is vital that the architecture be designed in a systematic fashion so that all issues are addressed openly and directly, rather than having the architecture evolve in an ad hoc fashion.

The IVHS architecture development methodology uses efforts of concurrent multidisciplinary public/private/academic teams. It requires contributors from many disciplines, including transportation analysts; systems engineers; and specialists in communications, information systems, infrastructure technologies, vehicle dynamics, data management, simulation, and modeling. Simulation and modeling are especially valuable for providing early indications of a user services cost/benefit ration, and thus early indications of the desirability of continuing to pursue development of a particular service.

DOT has initiated the National IVHS Architecture Development Program to develop the needed IVHS architecture. The program will proceed in two phases. Based on proposals submitted in April 1993, DOT has selected consortia led by Hughes Aircraft, LORAL-IBM, Rockwell International, and Westinghouse Electric to each develop an alternative IVHS architecture. Phase I will last 15 months from September 1993 to December 1994 and will result in multiple architecture definitions. The consortia with the most promising architectures will continue into Phase II. Lasting 19 months from December 1994 to July 1996, Phase II will focus on detailed evaluation of the remaining alternatives. Throughout both phases, the consortia will have the opportunity to refine their architectures as they gain further knowledge and insight. At the conclusion of Phase II in mid-1996, a national IVHS architecture will emerge.