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January/February 2000· Vol. 63· No. 4

The Customer-Driven Development of Human Factors Design Guidelines

by Christopher A. Monk and Joseph Moyer

Introduction
These days, drivers receive all kinds of information while they drive. New sources of information are appearing in cars and trucks with each new model year. In the fall, new high-tech in-vehicle devices make their way from the consumer electronics shows to the fall line-up's options list at your nearest car dealer. Primarily, these new devices offer some additional information or convenience to the driver. Systems such as collision and lane-departure warnings, route planning and navigation guidance, road signs, and communication via e-mail, fax, and cellular telephones are, or soon will be, offered by manufacturers and aftermarket vendors as options for the safety-conscious and comfort-seeking customer.

Needless to say, all this new information may present some serious distractions for drivers if not properly presented. For example, if a driver is following the route guidance provided by an in-vehicle navigation system, trying to decipher the route and street names from an electronic map display could be difficult and demanding.

The Federal Highway Administration (FHWA) undertook a six-year research program focused on issues related to in-vehicle information displays in order to provide design assistance to advanced in-vehicle systems engineers. The resulting product of this program is the highly anticipated, recently published Human Factors Design Guidelines for Advanced Traveler Information Systems (ATIS) and Commercial Vehicle Operations (CVO) (Publication No. FHWA-RD-98-057).¹

Producing useful human factors design guidelines was a significant challenge. By focusing on user requirements for both content and presentation, the ATIS/CVO design guidelines document is a success story in the production of design guidelines.

The guidelines were developed to aid in-vehicle information system designers to develop the user interface while considering its potential for driver distraction. In other words, the goal was to provide designers with key research-based guidelines that will reduce the level of distraction the driver experiences by using in-vehicle devices while operating a vehicle. Not only are these guidelines intended for new technologies in cars and light trucks, there is also a chapter dedicated to the specific needs of commercial truck drivers and to the kinds of information present in their cabs.

The challenge, however, was to produce a design guidelines document that would not sit on the designer's shelf and collect dust. This article describes how the guidelines are customer-driven and, therefore, are useful for designers. Examples of issues faced by in-vehicle system designers are presented along with the solutions provided by the guidelines to demonstrate their effectiveness and relevance.

The Problem With Guidelines

Figure 1 — Two-page layout used in the Human Factors Guidlines for ATIS and CVO.

Research can be difficult to translate into guidelines. In fact, it has been shown that guidelines and handbooks that follow more traditional formats do not maintain the interest of designers and engineers.² There is a history of producing guidelines that fail to consider both what is useful information for designers as opposed to researchers and how to present the guidelines in a more user-friendly format. This effort set out to develop design guidelines that successfully generalize existing research data into design parameters that meet the needs of designers.

Development of the Guidelines
A large-scale research program was initiated by FHWA to produce these useful human factors design guidelines for in-vehicle information systems (or ATIS). The effort included two phases: an analytical phase and an experimental phase.

The analytical phase consisted of a literature review, the identification of ATIS and CVO system objectives and performance requirements, a description of ATIS and CVO functions, a comparable systems analysis, a task analysis, a user characteristics and information requirements analysis, and the identification of the strengths and weaknesses of alternative display formats.

The empirical stage of this project included 11 laboratory experiments and three field studies. These empirical efforts focused on areas such as user stereotypes and acceptance, function transitions, in-vehicle information display, visual and auditory messages, multimodality displays, head-up displays, integration of collision-avoidance and ATIS information, ATIS under reduced-visibility conditions, driver response to unexpected situations when using an ATIS, and the effects of an in-vehicle ATIS on driver performance. In addition, two of the 11 experiments dealt specifically with commercial truck-related issues, such as driver fatigue and truck driver workload.

Once the information and data were collected, the real challenge of guideline production began. The process of synthesizing the results of the analytical reports and experimental data required careful consideration of the user's needs. To meet these needs, an exhaustive user requirements analysis was conducted.

User Requirements Analysis
One of the critical steps in developing these design guidelines was ensuring that the document was customer-driven. From selecting which guidelines ultimately were included in the document to the details of page layout and formatting, the user community was consulted, and customer input was solicited. In fact, FHWA actively pursued the input of engineers and designers working in the automotive industry.

The draft guidelines were distributed for review to 30 designers and engineers from automotive manufacturers and suppliers. Of the participants in the user requirement analysis:

• 25 percent were human factors researchers or practitioners.
• 75 percent were electrical, industrial, mechanical, software, and systems engineers with little or no human factors training.
• 100 percent had some responsibility for the content and layout of ATIS devices.
• 86 percent were involved in conceptual and/or detailed design of ATIS devices.
• 75 percent were involved in the test and evaluation of ATIS devices.
• 100 percent of the participants reported an urgent need for human factors design guidance in their ATIS design activities.
• Only 45 percent reported that there was any human factors input to their current ATIS design efforts.

*	Primary expert judgment
**	Expery judgement with supporting empirical data
***	Empirical data with supporting expery judgment
****	Primarily empirical data
Figure — Diagram showing recommended distances for final voice instruction prior to a turn.

The response from industry was overwhelmingly positive regarding its participation in the development of these guidelines. FHWA feels strongly that by performing this type of user requirements analysis, the end product is much more useful to in-vehicle system designers. Also, user input regarding the presentation format of the guidelines was invaluable.

Guideline Presentation
The guidelines are presented in a two-page format that includes a brief introduction, the guideline, a figure demonstrating the guideline or a table of recommended parameters, a four-star rating indicating the level of empirical support for the guideline, the supporting rationale for the guideline, cross references, and key references. Figure 1 shows the general layout of the two-page format.

The response to this guideline presentation style was exceedingly positive. In fact, the cross-references section was added as a result of a recommendation from the user requirements analysis.

Application Examples
System designers and engineers can proceed to generate a specification based on whatever information they have available, and then they can rely on the evaluation engineers to refine the specification. However, the availability and use of a design guideline based on research for a specific issue will save much of the effort and time of the design and evaluati—on engineers and will permit the reduction of the production schedule. By using the FHWA ATIS/CVO design guidelines, designers can save effort, time, and money.

The following two examples show both the relevance and user-friendliness of these design guidelines for in-vehicle information systems. Both problems are genuine and have solutions that can be found in the ATIS/CVO design guidelines.

 

Figure 3 — Diagram of an ATIS display showing information related to the coordination of truck destinations.

Instruction Timing
When designing an in-vehicle navigation and route guidance system with voice instructions, it is critical for engineers to determine a variety of specifications associated with voice instructions. These issues include the number of times a given instruction is provided prior to a turn or maneuver, the timing of the last instruction before the turn, the timbre and quality of the voice, speech clarity and speed, and message content.

Most of these issues can be resolved by design and evaluation engineers in a laboratory setting with the assistance of human factors specialists. However, the issue of instruction timing typically requires actual on-road testing to establish an appropriate specification. The difficulty is that this type of specification needs to be established prior to the evaluation of the product prototype. Therefore, assistance in establishing the specification for instruction timing is essential.

The number of times a guidance instruction is provided to the driver is also a complicated issue, but the critical element in this problem is essentially when to present the last or final instruction before the driver reaches the turning point. The reasoning behind this notion is that there will be times when a given road segment in the designated route is only long enough for the last guidance instruction to be presented. For example, if after turning onto Main Street, the route guidance system directs the driver to turn at the next street, which is one-eighth mile away, then the preliminary quarter-mile guidance instruction would not be presented.

Chapter five in the handbook is called Routing and Navigation Guidelines. By checking the chapter contents list, a designer could determine that Timing of Auditory Navigation Information is probably the guideline needed. Fortunately for the designer, this guideline provides detailed formulas for the timing of the last or final guidance instruction. Figure 2 shows the equation table and diagram for this guideline.

It is important to note that the timing guideline is based on the speed of the vehicle. For example, the ideal distance for the last instruction is (speed x 1.973) + 21.307 meters. Therefore, the specification can be tailored so that the system samples the current speed of the vehicle and then determines the appropriate timing of the instruction.

The engineers still have plenty of room for design creativity in this situation. The guideline is not dictating the design. The timing of the initial guidance instructions for a given turn is open to design flexibility. The critical aspect of this issue, however, was determining the appropriate timing of the final instruction. The guidelines provided invaluable research data in an easy-to-read and accessible form. Designers typically have little time to glean relevant data from appropriate research reports, let alone find such reports.

Destination Coordination Information
To maintain efficient schedules, operators of commercial cargo trucks need to coordinate loading and unloading times with their customers. This information is critical to truck drivers as they approach their delivery destinations. As one might imagine, delivery schedules are often dynamic due to the day-to-day fluctuation in number of shipments arriving and departing. Therefore, truck drivers and dispatchers usually communicate their current schedule status to each other to coordinate with the delivery site. The presentation of this status information in an in-vehicle display is an important issue because it is time-related information that is complex in nature. In other words, the driver needs to receive any schedule update right away in order to adjust his schedule.

The information, however, is not usually simple and brief. For example, the driver will not receive a message stating, "Behind schedule." The message will probably include the amount of schedule delay (e.g., 40 minutes) and a requested new arrival time. This is complex information that needs special presentation consideration.

Once again, the ATIS/CVO design guidelines publication is useful in this design situation. There is a guideline for the Presentation of Destination Coordination Information for commercial truck applications.

First, a visual display is recommended for this type of communications information. The guideline also allows the presentation of this information to the driver while the vehicle is in motion. This point is significant because several other types of information can only be presented when the vehicle is stopped. Finally, the recommended display format is a text description or iconic representation with a text label. Figure 3 shows the sample figure in this guideline.

It is important to note that this figure is not necessarily a recommended display arrangement. It is simply intended to demonstrate the application of the guideline. The purpose of the guidelines is to provide engineers with guidance and recommendations in their designs, not to prescribe rigid design requirements. In the current example, the designer may want to use icons consistent with other products from the same manufacturer. For example, a designer may have access to some standard icons within a catalog of the manufacturer's own design standards. The "Message From Dispatch" may be presented with such an icon.

Conclusion
This project has produced a useable and user-friendly human factors design guidelines document specifically tailored for in-vehicle information system designers. This was accomplished not only through good analysis and research, but also through the participation of some end-users in the process.

In fact, an additional benefit to tapping the customer for input during the development of this handbook is that the interest and demand for the product is already established. Several designers, engineers, and researchers have been asking about the formal release of this document for some time.

The document has already been used as a primary reference in the development of a Society of Automotive Engineers (SAE) Recommended Practice for in-vehicle navigation display. In addition, the ATIS/CVO guidelines will be a valuable reference for the development of in-vehicle systems to be included in the Intelligent Vehicle Initiative operational field tests to be conducted by the U.S. Department of Transportation (DOT) over the next few years.

References

1. Human Factors Design Guidelines for Advanced Traveler Information Systems (ATIS) and Commercial Vehicle Operations (CVO), Publication No. FHWA-RD-98-057, Federal Highway Administration, Washington, D.C., 1999.
2. J. Campbell, C. Carney, and B. Kantowitz. "Design guidelines for advanced traveler information systems (ATIS): the user requirements analysis," Proceedings of the Human Factors and Ergonomics Society 41st Annual Meeting, Vol. 2, pp. 954-958, 1997.

Christopher A. Monk is a research psychologist with Science Applications International Corporation. He works as an onsite contractor supporting the Human-Centered Systems Team's Intelligent Transportation Systems Program at the Federal Highway Administration's Turner-Fairbank Highway Research Center in McLean, Va. He has a master's degree in human factors psychology from California State University, Northridge.

Joseph Moyer is an engineering research psychologist and a member of the Human-Centered Systems Team in FHWA's Office of Safety Research and Development at the Turner-Fairbank Highway Research Center. He holds a master's degree in psychology from George Mason University.

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