Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: Comparable Systems Analysis
CHAPTER 10. PRELIMINARY HUMAN FACTORS GUIDELINES
INTRODUCTION
The objective for performing this comparable systems analysis was to compile lessons learned from exiting ATIS applications in the United States and to produce preliminary guidelines for the purposes of guiding empirical research to improve the design of future ATIS/CVO systems. Human factors design guidelines for ATIS/CVO systems represent the final product of the present contract. The preliminary guidelines from Task D, the comparable systems analysis, are one source of information that will feed into the process.
In Task F, Barfield et al. (1993) discussed the nature of guidelines and offered a four–star "guideline applicability rating system." The guidelines presented in this chapter do not fit conveniently into that rating system. They are "one–star" guidelines in that rating system, because they are based primarily on expert judgment rather than empirical data. However, the guidelines offered here are derived directly from ATIS and CVO or related systems. Perhaps Barfield's rating system should be modified slightly to include two independent dimensions: (1) empirical basis and (2) application domain similarity. There is little doubt that preliminary guidelines, even when based on subjective analysis, are more likely to be applicable and relevant when they are derived from actual ATIS and CVO systems rather than from different application areas. Different applications can involve many types of differences, such as system objectives, task demands, user population characteristics, and environmental factors. The following guidelines are based on ATIS/CVO comparable systems and are, therefore, directly appropriate. However, they are based on observation, expert judgment, user opinion, and other subjective analyses and should be considered preliminary. Empirical validation is needed before accepting them as guidelines.
The preliminary guidelines are sorted into somewhat arbitrary categories. In many cases, a preliminary guideline has implications for more than one of the categories. Each preliminary guideline is presented with a notation as to the lessons learned from which it was derived. That notation enables the reader to follow an audit trail for the lessons learned that was the source of the preliminary guideline.
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IN–VEHICLE DISPLAY DESIGN
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1. The orientation (north up or heading up) should be selectable by the user. When in the route planning mode, the default orientation should be
north up; when in the route guidance mode, the default orientation should be heading up. [UM12, NM19, SK06, TP13, CS02]
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2. The capability to preview a destination on a digital map should be provided to the user by map scale and slew (recenter) features, but the
system should be designed to prevent confusion about whether the map is showing current position. [CS08, NM03, TP14]
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3. Digital maps should be available to depict the user's current location, destination, and a recommended route, but are not the preferred method f
or depicting route guidance. [CS01, CS05, UM13, NM13, OM08]
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4. Digital maps should have a refresh rate that is sufficient to support smooth rotation of a heading–up display at any map scale during vehicle
turns. [CS14]
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5. Head–up display of computer–generated symbology is useful for avoiding the "eyes–in" vehicle problem, but should be
used only for critical information. [SK15]
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6. Displays of alphanumeric messages should include word–wrap, i.e., the display should not break one word onto two lines. [OM05] |
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7. Veiling glare should be minimized for all ATIS/CVO in–vehicle display applications. LCD displays, in particular, are susceptible to glare and
should have back lighting and contrast control. [OM01, OM02, OM03, OM04, NM23, NM24]
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8. Character size for in–vehicle displays should be large enough for the diverse driving population to read easily without undue visual search.
The minimum visual angle is a function of variables such as contrast, but is estimated to be approximately 0.30 to 0.45 degrees. [UM03, TT26]
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9. Only essential information should be included in in–vehicle displays to prevent display clutter and increased visual search time.
[NM09, UM13]
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10. In–vehicle displays should be mounted as near as possible to the driver's normal line of vision (high, center) without obscuring any view
of the roadway or outside terrain. [NM15, OM20]
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11. Color coding is useful to convey information such as recommended route, danger areas, or areas of traffic congestion. Color coding should be
used judiciously and according to accepted human factors standards for display design. [UM01, NM14, SK01, SK05]
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12. Speech output should be used in conjunction with visual displays for route guidance, although the user should be given control
(on/off and volume) over the speech output system. [TT09, TT11, NM26]
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13. Speech output can be used to identify the location of hazards, to provide information about vehicle status, and to indicate cautions and
warnings, but should not be used to confirm routine events. [UM05, UM06, SK02]
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14. The syntactics and semantics of both speech and alphanumeric messages should be tested with the target user population for intelligibility
and comprehension. [TT22, UM06, SK07, TT10]
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CONTROLS
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15. Controls for ATIS/CVO systems should be designed for ease of use to minimize the time and attention required of the driver. [TT16, TT17, OM16]
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16. Buttons on the steering wheel should be considered as a viable design option because they are easy to reach. [TT17, SK16]
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17. Touchscreens on a digital map provide the ability to designate a location with one touch. [CS10]
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18. Touchscreens should be designed to resist fingerprints and smudges and should be robust to calibration error. [CS12, CS13]
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19. Entering an alphanumeric character should not require more than one button push. [TT16]
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20. Adequate user feedback (tactile, auditory, or both) should be provided for each button press or control input. [NM06]
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21. ATIS/CVO in-vehicle display and control components should tolerate fluid spills, such as beverages, without affecting system operation. [OM06]
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USER–SYSTEM INTERFACE
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22. If an expert system is included in an ATIS/CVO system, the responsibilities of the driver and the system must be clearly understood. No action
should be taken by the expert system (such as slewing the map) without the knowledge and permission of the driver. [SK08, SK10]
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23. If an intelligent navigation aid recommends an alternate route, the reason for the recommendation and the time of the calculation should be
conveyed to the driver or conveyed upon request. [SK04]
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24. An intelligent navigation system should develop a model of the driver to anticipate when assistance may be needed and what criteria may be
appropriate (speed, safety, travel time, scenic beauty, etc.). [SK04, SK11, SK13]
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25. Display mode changes should either be under direct control of the driver or should be selectable in advance as defaults. [NM12]
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26. The status of the major system components, modes, selectable features, and computer should be indicated or available upon request. [NM10, CS09]
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27. Driver interfaces to ATIS/CVO systems should be consistent in format, location, and content. [UM02]
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28. An easily perceived indication should be given quickly to a driver who departs from a recommended route while in route guidance mode. [NM08]
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29. The driver should be given the option to reject a recommended route (for any reason, such as recent knowledge of road closure) and the system
should calculate an alternative. [NM04]
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DRIVER ATTENTION / WORKLOAD/SAFETY
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30. The use of ATIS/CVO systems, compared to traditional navigation methods, should not increase the driver's attentional demands and mental
workload during driving tasks and should not compromise safety. [TT05, TT06, TT23, OM18, UM04]
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31. While the vehicle is in motion, the interface design should reduce driver workload through restricted access to control functions, guidance
screens rather than maps, and supplementary use of voice output with the visual display. [TT23, UM04, NM26]
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32. Maintaining the driver's normal attention directed towards the out–of–the–windshield scene should be fostered by mounting
ATIS/CVO displays as close to the origin of optic flow without obstructing the view of other in–vehicle equipment or outside objects.
[OM19, OM20]
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33. ATIS and especially CVO systems should incorporate a structured training program that provides the ability of repeated "hands–on"
practice and increased automation while reducing attentional demands. [TP25]
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DRIVER INFORMATION REQUIREMENTS
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34. ATIS/CVO systems should provide the driver with information about roadway hazards and traffic congestion. [UM07]
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35. CVO systems should include a paging system to inform drivers of incoming priority messages when they are not in their vehicles. [OM24]
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36. Real-time distance to a turn should be integrated into ATIS route guidance displays. [NM33]
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37. Route turn information should reflect the physical characteristics of the roadway. [NM31]
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38. ATIS/CVO systems should provide text-based route guidance if graphic displays are not viable. [OM11]
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39. Automatic and manual emergency aid and road–assistance request features should be designed to function with a backup power source. [OM13]
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40. Motorist services information is highly valued by ATIS users. [TT14]
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ROUTE GUIDANCE / PLANNING / NAVIGATION
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41. ATIS/CVO systems should allow drivers to navigate with a map display without entering a destination. [TT13]
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42. Route planning functions should be fully integrated with route guidance and navigation functions when designing ATIS/CVO systems. [CS11]
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43. Route navigation displays should clearly depict the selected route to a destination by using thicker street lines, color coding, or other
distinguishing features. [NM14, UM14]
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MAP DATABASES
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44. ATIS/CVO map and directory databases should be updated frequently to maintain a current system that reflects roadway and destination
changes. [NM11, TP18]
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45. ATIS/CVO planned routes should account for one–way streets and two–way streets with a center divider. [NM02]
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VEHICLE LOCATION ACCURACY
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46. Accurate vehicle location is fundamental and essential for effective ATIS/CVO systems. Engineering design teams should ensure accurate vehicle
location even under worst-case conditions. The user interface should inform drivers (and dispatchers, for CVO systems) as to significant decrements in
location accuracy. [NM07, TP15, TP21]
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DRIVER ACCEPTANCE
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47. The design of ATIS user interfaces should incorporate the following features to increase driver acceptance: voice plus visual route guidance,
selection of alternate routes, and both map and guidance screens. [TT01, TT08, TT09, TT12]
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48. Criteria for user acceptance of ATIS systems include: reduced trip planning time and travel time; safety should not be degraded; the number of
turn errors should be reduced. [TT02, TT03, TT06, TT07]
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49. To increase driver acceptance of CVO systems, the system should outperform current dispatch-driver communication methods (e.g., finding
a phone to call dispatch). [OM08, OM23]
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COMMUNICATION BETWEEN DRIVER AND DISPATCH / HELP CENTER
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50. CVO in-vehicle displays should indicate when a dispatcher receives and accesses a driver-transmitted message. [TP22]
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51. CVO systems, including emergency response vehicle systems, should provide both the driver and the dispatcher with estimated time
of arrival (ETA) to the destination. [TP16]
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52. ATIS/CVO systems should have adequate manuals and/or reference materials to answer problems, or "on-line" help should be made available
as an option for cellular phone users. [OM22, TT18]
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53. ATIS systems should provide the driver with the ability to transmit free–format and/or pre–defined messages to a dispatch center
via the in–vehicle display in CVO applications. [OM23]
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TRAINING ISSUES / REQUIREMENTS
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54. Training should be provided for new users of ATIS/CVO in–vehicle systems. The amount of training time required to use an ATIS system
efficiently should take no more than 1 hour. For CVO systems, 4 to 8 hours is acceptable, depending on the complexity of the system.
[NM16, TT24, OM22, TP25]
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55. ATIS/CVO brochures and driver manuals should be easy to understand and easy to reference when drivers need to find information. Other
training and job aids, such as audiotape and on–line tutorials, may be appropriate. [OM22]
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HANDBOOKS AND GUIDELINES
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56. ATIS design team members should be made aware that human factors design handbooks and literature exist and can assist in the design
process. [OM26, TP02, TP05, TP12]
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57. Human factors guidelines should provide design information regarding mental workload, attentional demands, situational awareness,
and time–sharing requirements in the use of ATIS/CVO systems. [TP11]
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58. ATIS/CVO interface design criteria should be based on the usability and safety of the system, anticipated environmental abuse,
crashworthiness, ease of installation, cost to the user, and driver acceptance. [OM28, OM29, TP04]
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59. ATIS/CVO brochures and manuals should provide essential directions for using the system, presented in a format and style that is easy
to understand. [OM22, NM17]
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DESIGN APPROACHES
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60. Iterative usability testing, based on rapid prototypes, should be done early in the design of ATIS/CVO systems. [TT21, CS19, UM01, TP07, TP08]
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61. Subject Matter Experts (SME's) representative of the projected user population should be included throughout the design of ATIS/CVO
systems. [CS18, SK17]
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62. A design team should include human factors and systems engineering experts throughout the design of ATIS/CVO systems. [TT19, TT20, CS03, CS17]
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63. Operator–in–the–loop simulation is recommended as a test and development tool during the development of ATIS/CVO systems.
[SK18]
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64. Careful attention should be paid to the definition of performance measures and measures of effectiveness to be used during system development,
testing, and evaluation. [UM15, SK19, CS20]
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65. Evaluation of the benefits of ATIS/CVO systems should be done with reference to baseline methods for accomplishing the same functions
(e.g., paper maps for route guidance). [UM08]
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66. Cost–benefit analysis and a customer–driven approach are essential parts of an overall design process and should include human factors
analysis of user requirements and user–interface design. [TP24, OM25, TT19]
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FHWA-RD-95-197
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