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Publication Number: FHWA-RD-96-177
Date: October 1997

Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: Definition and Prioritization of Research Studies

 

APPENDIX A: STUDY/ISSUE SOURCES

 

NINE MOST VITAL STUDIES/ISSUES

Below, we provide more comprehensive descriptions of the nine most vital studies/issues identified in this effort. These descriptions have been adapted from previous project reports.

A1 Examine the cognitive demands placed on the driver by the need to transition from one ATIS function to another. [Task C]

Few of the subsystem functional characteristics associated with ATIS/CVO will operate in the absence of others. Instead, most ATIS/CVO systems will contain several functional characteristics. To the extent that these systems represent an integrated set of functional characteristics, they will be more likely to enhance driver performance compared to independently installed functional characteristics. Therefore, as part of the description of each functional characteristic, we must consider the potential interactions between functional characteristics that may inhibit or facilitate their effectiveness.

Interactions between functional characteristics might stem from the information requirements of each function or from human cognitive characteristics. For example, route selection requires information concerning the location of the destination, and a services/attractions directory provides information about potential destinations. Therefore, these functions would facilitate each other. In other circumstances, human information-processing limits may introduce interactions between functional characteristics that might inhibit their effectiveness. For example, the display of commercial information may overwhelm drivers with information and inhibit the effective communication of emergency or warning information. In contrast, careful integration of several functions may minimize redundant information that might otherwise overwhelm drivers. For example, integrating in-vehicle guidance signs with route guidance information might minimize extraneous information, while better supporting the driver's navigation on an unfamiliar route. This situation represents a case where a pair of functions might either inhibit or facilitate each other, depending on the final system design.

A4 Identify how complex interactions among ATIS functions might affect driver understanding and response to the system. [Tasks C, A]

Few of the subsystem functional characteristics associated with ATIS/CVO will operate in the absence of others. Instead, most ATIS/CVO systems will contain several functional characteristics. To the extent that these systems represent an integrated set of functional characteristics, they will be more likely to enhance driver performance compared to independently installed functional characteristics. Therefore, as part of the description of each functional characteristic, we must consider the potential interactions between functional characteristics that may inhibit or facilitate their effectiveness.

Interactions between functional characteristics might stem from the information requirements of each function or from human cognitive characteristics. For example, route selection requires information concerning the location of the destination, and a services/attractions directory provides information about potential destinations. Therefore, these functions would facilitate each other. In other circumstances, human information-processing limits may introduce interactions between functional characteristics that might inhibit their effectiveness. For example, the display of commercial information may overwhelm drivers with information and inhibit the effective communication of emergency or warning information. In contrast, careful integration of several functions may minimize redundant information that might otherwise overwhelm drivers. For example, integrating in-vehicle guidance signs with route guidance information might minimize extraneous information, while better supporting the driver's navigation on an unfamiliar route. This situation represents a case where a pair of functions might either inhibit or facilitate each other, depending on the final system design.

One must zoom in/out and pan to various locations to plan a route prior to starting the drive. However, particularly for complex or long routes, it is difficult and time consuming to plan a route in this manner. What generally happens is that drivers, after inputting a desired destination, drive immediately and plan the route in large part as they travel. This strategy increases the attention demand of the composite driving task, since pre-drive planning has now been allocated as an in-transit task (Antin et al., 1990). Dingus et al. (1989) therefore recommend that a provision for route selection be provided as part of navigation and information systems. Another advantage to providing a route selection algorithm as part of navigation system features is that many more options are available for information presentation. If no route is provided, an area map must be displayed to accurately navigate. If a route is provided, the navigation information can be displayed aurally and/or visually, textually or spatially; the information can also be displayed in a turn-by-turn graphic format or an entire route graphic format.

B3 Identify how the information drivers need and want from road sign (ISIS) and warning systems (IVSAWS) might influence behavior. [Tasks D, F]

There is not a good understanding of which pieces of information about a traffic problem are necessary and useful to drivers. Specifically, it is not clear whether knowing about lane closures, or the cause of a congestion problem, will cause drivers to modify their behavior. Perhaps it is beneficial to suppress clarification of a spectacular incident like a fire, as it could encourage gawkers to travel to the scene. On the other hand, it also alerts drivers to the possibility of emergency vehicles in the area.

There are a variety of ways to express the severity of a congestion problem. Terms like "heavy traffic," "sluggish traffic," "a one minute delay," "bumper to bumper," "stop and go," "slow and go," and "merging delay" are used in traffic reports broadcast by radio stations. Radio traffic reports also occasionally provide an estimate of the length of a congestion queue. More research is needed, however, to determine how drivers use an estimate of a backup queue; whether it can be reliably estimated; and how best to describe it to drivers: in miles, or number of traffic signals, or from street X to street Y. The word "congestion" itself may be ambiguous; Do drivers interpret it consistently as slow traffic, or can congestion also refer to a heavy volume of traffic moving at the posted speed? The location of a traffic problem can also be expressed in various ways. Can the relevance of the problem be assessed more easily by the driver if its location is described relative to the vehicle or in absolute terms?

Onboard computer-generated traffic advisories can provide information on demand which is filtered for relevance to a given vehicle location/route. Some issues which arise when filtering for relevance strategies are considered include the criteria which are applied to determine relevance; the upper limit on the amount of information which should constitute an on–demand traffic report; and the possibility of giving drivers the ability to tailor traffic reports to their own needs and interests (Means, et al., 1992).

C4 Examine how information reliability (e.g., false alarms) influences driver adaptation and enhances the potential for an improper response to ISIS/IVSAWS. [Tasks B, A]

ATIS devices must provide accurate and reliable real-time information. Specific issues that have been raised in this regard include: (1) the tolerance of private vehicle drivers' for congestion data that is out of date, (2) the need to decrease the current time between the occurrence of congestion and the incorporation of that information into in-vehicle systems, (3) the possible utility of providing confidence levels for estimated travel times, and (4) providing the driver with the data upon which alternate routes are recommended.

In general, ATIS research is lacking for IVSAWS and ISIS applications. Although these ATIS systems will probably not have particularly complex user interfaces, they present unique human factors and safety issues. IVSAWS will be an alarm type of display; therefore, issues of timing, modality false alarms, and potential operator reaction must be addressed.

C5 Investigate how to display multiple ISIS and IVSAWS messages so that drivers can identify relevant information and react appropriately. [Task F]

In this context, information refers to the mathematical construct discussed by Fitts and Peterson (1964) and is analogous to the reduction in uncertainty that accompanies a choice among the alternatives. A specific example in the context of an ATIS system might address the effects of a proliferation of warning icons that warn of hazardous road conditions. As the number of icons and warning messages increases, the time to respond will increase as a linear function of the information content of the warning icons. At one extreme, many equally likely alternatives will maximize information content, increasing response time, while a single choice minimizes information content and minimizes response time.

D2 Identify features that will benefit/require standardization across many types of ATIS systems and functions. [Tasks D, F]

Driver interfaces must be consistent. Information communicated to the driver in visual displays should be consistently located within the display. Vocabulary used in auditory speech displays should use a consistent syntax and sequence of information.

Similar to population stereotypes and innate response tendencies, automatic response developed through experience with a consistent interface design can enhance performance, while an inconsistent interface design can lead to increased errors and response times. Like population stereotypes, interface design consistency affects performance because of learned expectancies rather than innate characteristics of the users. In contrast to population stereotypes, the effects of interface design consistency are specific to a narrow domain (such as computer operating systems or vehicle controls), while population stereotypes span a wide variety of domains (e.g., red frequently signifies danger in a wide variety of settings). Consistency associated with design standards facilitates understanding of new systems based on experience with other systems, and promotes efficient performance through well practiced, consistent stimulus-response mappings. Schneider and Shiffrin (1977) showed that after extended practice with consistent stimulus-response pairings, subjects developed automaticity in their responses and were able to respond with little conscious effort. Inconsistent mappings did not promote automaticity as reflected by less accurate performance. The development of automaticity for searching displays takes somewhat longer in older than young adults (Fisk & Rogers, 1991), suggesting that performance even with well-designed, compatible displays will be less effective for older drivers.

D4 Examine the performance differences associated with focusing all ISIS and IVSAWS information through either single or multiple display channels. [Task G]

Wickens (1987) emphasizes the importance of coding display information redundancy in different modal formats. Redundant presentation of information in the auditory and visual modalities will accommodate transient shifts in noise within the processing environment (e.g., visual glare, background noise, verbal distractions), which may influence one format or another. Display format redundancy also accommodates the strengths of different ability groups in the population (e.g., high spatial ability versus high verbal ability).

Unfortunately, no specific guidelines for tactile displays can be given. It can only be stated that an effort should be made to encode manual controls with tactile information. This will enhance feedback and enable drivers to manipulate controls without taking their eyes off the road. Designers of in-vehicle systems should seriously consider the use of tactile feedback displays. There is a great need to perform research relevant to the use of tactile displays, in order to further define their value.

D12 Evaluate the effectiveness of multimodality displays, such as voice in combination with text. [Tasks A, F, G]

The implications of employing multimodal displays to aid map interpretation and navigation while driving are largely unknown. In particular, the driver's ability to read and understand navigation information from maps, symbols, and text, in various combinations is of interest.

While hearing does not play as central a role in driving as does vision, its importance may increase as sound is used to convey information to the driver without jeopardizing the driver's view of the road. In particular, sound offers an alternative to HUD's and other visual displays because it does not compete for visual attention. For example, Walker et al. (1991) report that drivers using auditory navigation devices drove more safely than those using visual devices. Subjects using visual devices missed more gauge changes, had longer reaction times, and drove more slowly than subjects using auditory devices. Although auditory information avoids the human limitations of vision, human hearing has a number of limits that may have significant implications for ATIS systems.

Driver overload has consistently been identified as a concern associated with the use of multimodal displays. If the limits of working memory must be exceeded to display all of the necessary information, the system should include a method of recalling or re-presenting the information at a later time. Displaying this information both visually and aurally would in many cases enable the driver to receive the information without adding to the visual attention load. In addition, the information could be recalled at a later time if it is forgotten or misunderstood. It is very important to minimize the complexity of displays in a signing system, because the system will be functioning almost entirely while the vehicle is in motion. Any unneeded information that is displayed will require more attention by the driver that could create an unsafe condition.

D17 Identify specific concerns regarding how display formats and modality impact CVO driver workload. [Tasks C, A, G]

There are a number of concerns associated with CVO driver overload. First, CVO's typically have more components involved in the operation of their vehicle. For example many trucks have power take-off assemblies or refrigerator units. Thus, the required monitoring may be more complex because of the additional systems that require monitoring. Therefore, when designing the interface, the complexity of information presented to the CVO driver must be considered.

Second, it is unclear what sensory display modes and what associated information format and density are most appropriate for each of the ITS functions. Information from visual displays should be coded to allow for aggregation from successive glances. Timing of information presentation includes speed, control activation, traffic density, headway, weather, driver characteristics such as age and ability.

Third, a combination of a HUD and a centrally located video dashboard display may provide the optimal method of displaying visual ATIS information. Despite its advantages, this display option will be the most expensive to include in the automotive environment. In the case where such cost is beyond the constraints of a given design, either a HUD or centrally located dashboard display are attractive choices. An issue that still remains with respect to any of these options is visual display format selection. In addition to the format issues described in the above section, HUD's need to be analyzed for their compatibility with the display format that is chosen and the quantity of information provided. The current state of HUD technology does not allow the effective display of the amount of detailed information found on full route maps. Information requirements that are simpler and require more frequent glances, such as icons and alphanumerics, are more suited to display on a HUD. Information that requires more display resolution and possibly color coding should be allocated to display on a video screen.

 

FHWA-RD-96-177

 

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