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Publication Number:      Date:  Winter 1995
Issue No: Vol. 59 No. 2
Date: Winter 1995


Human Factors in Advanced Traffic Management Systems

by Nazemeh Sobhi


Today's traffic centers control traffic signals in a relatively low-tech environment. However, this situation is fast changing. The traffic management centers (TMCs) of the near future -- under the Advanced Traffic Management Systems (ATMS) component of the Intelligent Transportation Systems (ITS) program -- will be sophisticated facilities with advanced tools and communication systems, manipulating and managing massive amounts of information.

The advanced TMC will help in the real-time management of traffic, including monitoring and controlling roadway access, responding to and managing incidents, rerouting traffic, and communicating and coordinating with the public and the media. It will perform these functions with advanced ITS technology such as sophisticated sensors; data fusion, information processing, and communications equipment; and technology to automate routine decision making and other activities.

TMC operators will have more and better data with which to work than ever before, and they will have a broader range of options for controlling or influencing traffic flow. They will have to interpret incoming information; determine and implement measures to ensure effective traffic flow; and work with various agencies to detect and remove accidents, stalled vehicles, and other incidents that create congestion. These new capabilities and responsibilities far exceed those of today's TMC operator.

Experience -- gained through the automation of the airplane cockpit and the centralized control room -- shows that introducing advanced tools and systems into a previously manually based work environment poses significant human factors challenges. Early phases in the cockpit's evolution were costly ones in terms of human performance, system-induced human error, and accidents. Since then, a new discipline of human factors engineering has arisen to address the human factors problems associated with data display, system integration, and worker performance, among others.

Perhaps the most important lesson learned in previous low-tech to high-tech system conversions is the importance of applying human factors principles and methods early on in the project. An automated system imposed on human workers will not and cannot succeed. A system designed for human users can and will succeed.

To this end, researchers are studying the human factors interface with the higher technology of ATMS in several studies under a "Human Factors in ATMS Design Evolution" contract that was awarded to Georgia Tech Research Institute (GTRI) in fall 1992. These studies include human factors issues in overall system design and function allocation, user interface design, automation approaches, organization design, and operator's capabilities and limitations.

The ATMS Human Factors Contract

Operators sometimes make mistakes while doing their jobs. The design of jobs and systems, however, can have a strong effect on the frequency and significance of these mistakes. The key human factors rule in designing a complex human-machine system, such as the TMC, is to minimize human and system errors and to optimize operator and system performance.

TMC system designers need answers to a broad range of human factors questions. Answers to some of these questions may come from working experience with human factors issues in existing TMCs or other kinds of comparable advanced control rooms. Developing certain design guidelines, though, will require empirical data. Therefore, GTRI researchers are tackling the human factors aspects of the ATMS TMC design project from two main fronts:

The main products of the GTRI project will be a human factors design handbook to guide the designers and users of TMCs and a real-time, interactive TMC simulator. Other products will include documented information on all systems engineering design processes, multipurpose database software for future in-house studies, and recommendations for upgrading the simulator for future testing of human factors issues in more sophisticated ATMS TMCs.

The remainder of this article describes the status of the GTRI project and its deliverables.

Systems Engineering Design

The systems engineering aspect of the GTRI project will produce a detailed series of analyses that define a set of TMC objectives, the functions necessary to meet these objectives, opportunities for full or partial automation of the functions, and operator performance requirements and tasks within the partially automated TMC. System automation should be designed to assist and support the traffic management decisions made by the operator. Poor automation can increase the operator's workload and can induce frustration and faulty decisions.

So far, researchers have completed the first of these analyses. They have identified the following objectives for the TMC:

Next, the researchers will conduct a functional requirements analysis based on these objectives. What discrete, specific functions are needed to fulfill each objective? For example, fulfilling the first objective requires the capability to assess current traffic and roadway conditions. To assess current traffic conditions, in turn, implies an ability to determine location, speed, and type for each vehicle on the roadway system or for a representative sample of those vehicles.

Once all functions implied by the objectives have been identified, the next step is to allocate those functions to either humans, machines, or a combination of both. Finally, the researchers will determine how well the operator performs the allocated tasks and will decide what is necessary to optimize operator and system performance.

A GTRI researcher at an operator work-station.

A GTRI researcher at an operator work-station.

Human Factors Research Simulator

The ATMS human factors research simulator consists of the following components:

The simulator emulates a wide variety of inputs, outputs, and operator support systems. For example, it emulates inputs from traffic and roadway sensors, closed circuit television monitors, voice communication systems (including cellular phones), probe vehicles, and database services. It also emulates outputs to intersection control devices and algorithms, roadway access devices and control algorithms, variable message signs, traffic bulletin boards, commercial radio and television stations, cable television traffic channels, highway advisory radio channels, and voice communication systems.

ATMS operators can observe accidents via video surveillence cameras, call for assistance, and complete accident incident forms all from their monitor.

ATMS operators can observe accidents via video surveillence cameras, call for assistance, and complete accident incident forms all from their monitor.

Development of Design Guidelines

A comprehensive program of human factors research began in June 1994 to help develop design guidelines for future TMC designers and users. The research issues fall into four basic categories: equipment configuration, human-machine performance, job design, and operator training.

Equipment configuration

his study area includes questions about how individual controls and displays should be configured and how control rooms should be organized and arranged. Some candidate issues for experimentation via the human factors research simulator are:

Human-machine performance

This study area addresses questions about operator capabilities and limitations in performing different tasks in TMC, with or without machine assistance. Some candidate issues for experimentation are:

Job design

Included in this study are questions about how the various tasks that are required of operators should be combined and assigned to specific staff positions. Some candidate issues for experimentation are:

Operator training

Included in this study area are questions about which operator skills and abilities are required to perform assigned tasks and what team training is needed. Some candidate issues for experimentation are:

Human Factors ATMS TMC Design Guidelines Handbook

A primary product of this research is a comprehensive design handbook of recommendations and guidelines for the designers and users of the future ATMS TMC. This handbook is being developed in two phases. In the first phase, which was completed last summer, analytic data was obtained through: (1) visits to approximately two dozen TMCs and other operational command and control centers and (2) interviews with TMC experts in the United States, Canada, and Europe. Based on these findings, a draft handbook is being prepared. This draft will be modified and refined based on inputs from the study's second phase. During the second phase, empirical data will be obtained by testing technologies and conducting comprehensive human factors experiments on the ATMS research simulator. The resulting final handbook of design standards and guidelines will be available by December 1995.


The Federal Highway Administration's human factors research program in ATMS is designed to meet the current and projected needs of the TMC design community. Design guidelines are developed based on user requirements and analytical assessments of existing TMCs and comparable systems. The first edition of the human factors ATMS TMC design handbook will be available before the end of 1995, in time to support current upgrades and designs of TMCs. The human factors TMC research simulator supports the development of empirically based human factors design guidelines. This research test bed will continue to support the development and refinement of ATMS TMC design well into the future.

Nazemeh Sobhi is a highway engineer in the Office of Safety and Traffic Operations Research and Development, Federal Highway Administration. Her expertise is in the human factors aspects of intelligent transportation systems. She received a bachelor's degree in computer science from Radford University in 1987 and a master's degree in transportation engineering from the Virginia Polytechnic Institute and State University in 1989. Currently, she is a doctoral candidate in civil engineering at the University of Maryland.




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