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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
Commercial Vehicle Scenarios
Commercial Driving Scenarios Based on Frequency Count and Centrality Measure
The frequency count analysis and the centrality measure analysis showed that dynamic route selection was the functional characteristic that had the greatest number of interactions with other functions, while dispatch was considered the most central. In addition to these two measures, route scheduling and road condition information were also considered quite central as well.
Scenario C12 (shown in table 50) was chosen because it included three of the most central and most frequently interacting functional characteristics (5.3, 8.2, and 9.2). In addition, this scenario illustrates the interactions between two different subsystems, while accentuating CVO–specific characteristics.
Table 50. Description of Scenario C12.
Commercial Driving Scenarios Based on Functional Clusters
As indicated in the private scenarios section, this cluster analysis organizes the functional characteristics into five pre–specified groups (clusters). In the case of the commercial scenarios, out of the five specified clusters, four of them had a meaningful relationship. The first cluster has been labeled Resource Management and Planning as it groups functions that related mostly to fleet resource management and dispatch. The second cluster is called Navigation and Route Guidance and includes both IRANS and ISIS functions, except for the immediate hazard warning from IVSAWS. The third cluster is concerned with Regulatory and Administration Coordination as three of its functions are related to the regulatory or administrative agencies. The fourth cluster was not included in this analysis, as it was indicated in the function selection section of this document. Finally, the fifth cluster is named Services Request because it includes the functional characteristics related to services and attractions as well as the manual aid request function. For each one of these clusters, a scenario has been chosen that illustrates one particular situation. As mentioned previously, these scenarios are only one example of the many mapping between functional characteristics.
Cluster 1. This cluster has functional characteristics that span across three different ATIS subsystems, in addition to some of these functions being specific to CVOs. This cluster of functions is the largest of the four, grouping on the overall seven functional characteristics. A description of Scenario C13 is shown in table 43.
Table 51. Description of Scenario C13.
Cluster 2. This cluster focuses mainly on navigation and route guidance. The functions, once more, originate from three different systems (IRANS, ISIS, and IVSAWS). Scenario C4 was chosen as it includes four out of the five functional characteristics that make up Cluster 2 (see table 52). It is also interesting to note that the functional characteristics that make up this cluster (5.4, 5.6, 7.1, 7.2, and 8.1) are not specifically related to CVO operations.
Table 52. Description of Scenario C4.
Table 53. Description of Scenario C11.
Cluster 5. Scenario C15 (see table 54) facilitates mainly the service directory and aid request. Most of the functions included in this cluster are related to IMSIS and IVSAWS. This cluster is important to consider as it represents two ATIS subsystems that support both the private and the commercial industries. Considering that the scenarios generated initially in Task B included, for the most part, a very limited number of functional characteristics, it was necessary to create a new scenario that would include more than one or two functions.
Table 54. Description of Scenario C15.
Commercial Driving Scenarios Based on the Nature of Task Interactions
The nature of task interactions remains the same whether or not the environment is private or commercial. In fact, regardless of whether the driver is operating in a private or a commercial vehicle, the order with which he or she will accomplish the various driving–related and ATIS–related tasks will not vary. In either case, some of the functions will interact in a sequential manner, while others will either branch out or be recursive. As a consequence, it seemed repetitive to create commercial driving scenarios that would illustrate each one of these interactions, especially considering that the above four scenarios summarized them. A similar conclusion was reached for the scenarios requiring high workload demands.
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Keywords: Advanced Traveler Information System (ATIS); Commercial Vehicle Operations (CVO); Intelligent Vehicle-Highway Systems (IVHS)
TRT Terms: Highway communications, Trucking--Technological innovations, Trucks--Communications systems, Advanced traveler information systems, Commercial vehicle operations, Human factors