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Publication Number: FHWA-RD-95-176
Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: Task Analysis of ATIS/CVO Functions
APPENDIX B. FUNCTION AND SCENARIO SELECTION
One of the main goals of the task analysis is that it be a systematic, top–down analysis of the tasks performed by users of ATIS/CVO systems in order to meet the required functions of each system. The task analysis should describe the set of tasks that a driver would have to perform in a realistic driving environment. These tasks include both driving–related tasks and ATIS/CVO–related tasks. To study the interactions between these two sets of tasks, it is necessary to have a fairly realistic setting. However, because these systems do not fully exist, it was useful to create fictional scenarios that would provide the context of a realistic environmental setting in order to explore how these two sets of tasks could interact.
Task B generated several scenarios, both for private and commercial operations. The purpose of these scenarios was to aid in the identification of ATIS features and functions, as well as to support the task analysis effort. The scenarios in Task B were not based on comprehensive analyses of ATIS features and functions, nor on a comprehensive analysis of the task of driving with the aid of an ATIS. In fact, they were created to represent a broad sample of the driving scenarios identified by the transportation community as part of the Task B effort. In general, they summarize the issues, capabilities, functions, and features specific to each one of the ATIS/CVO systems as identified during the course of Task B interviews.
Unfortunately, the conceptualization of these scenarios occurred before the completion of Task C, the purpose of which was to identify functional characteristics for each of the ATIS/CVO systems. In addition to identifying functional characteristics, Task C contributed to each of these scenarios by illustrating how each scenario draws upon a set of functional characteristics. Table 38 shows the functional characteristics used in the private vehicle scenarios, while table 39 shows the same breakdown for the commercial vehicle scenarios.
These two tables show two important facts. First, the scenarios developed in Task B do not span the entire range of functional characteristics. Some functional characteristics are not illustrated at all. For example, table 38 for private vehicle scenarios shows that as many as eight functional characteristics (5.2, 5.4, 5.7, 6.1, 6.3, 6.4, 7.1, and 8.3) were not considered in the conceptualization of these scenarios. Similarly, table 39 for the commercial vehicle scenarios shows that as many as nine functional characteristics (5.1, 6.1, 6.3, 7.1, 7.2, 7.3, 8.5, 8.6, and 9.4) failed to appear in any of the scenarios. Second, almost all scenarios showed an integration of more than one functional characteristic or ATIS subsystem into one situational context. As pointed out in Task C, this illustrates the importance of closely examining the interactions between functions to identify the coupling of various systems. By knowing how the functional characteristics interact within a subsystem or across systems, it will be possible to provide meaningful guidelines for the design of integrated ATIS/CVO systems rather than create a disconnected collection of independent functions and subsystems.
Considering that several functional characteristics failed to appear in the scenarios of Task B, it may be useful to enhance the scenarios in the context of the full list of functional characteristics developed in Task C. As a consequence, the initial set of scenarios was expanded, and the functional characteristic breakdown for each one of the new private vehicle scenarios is summarized in table 40, while the one for the commercial vehicle scenarios is reviewed in table 41.
Table 38. Functional characteristics used in private vehicle scenarios as originally designed in Task B.
Table 39. Functional characteristics used in commercial vehicle scenarios as originally designed in Task B.
Table 40. Functional characteristics used in the expanded private vehicle scenarios.
Table 41. Functional characteristics used in the expanded commercial vehicle scenarios.
Scenarios Selected for Analysis
Scenarios involving both private vehicle operations and commercial vehicle operations were selected to optimize the efficiency of the analysis. Scenarios were selected based on their representativeness in terms of the analysis that was done on the relative importance of functions as determined by information interactions and to represent several specific characteristics of the dynamic driving task that are likely to be of particular importance to an understanding of the way that drivers will interact with ATIS/CVO.