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Publication Number: FHWA-RD-95-176
Date:November 1996

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.

PURPOSE To illustrate the functional characteristic that had the greatest frequency count, dynamic route selection, and the one that was considered the most central, dispatch.

SUMMARY It is Friday evening, during rush hour traffic, just before a holiday. The commute is slow because it is snowing and several accidents obstruct the traffic circulation. A central dispatcher for medical aid vehicles in a large metropolitan area is working her normal evening shift. She receives two concurrent emergency calls for aid required at a freeway accident and a private residence. The dispatcher enters the locations of the emergencies into her routing system and the system determines the appropriate medical aid vehicle stations to call and the appropriate routes to take, based on the fastest predicted travel time under current traffic and road conditions. Upon reception of that information, she informs the appropriate drivers of the new destination and route to take. The drivers enter the routing into their ATIS and activate IVSAWS to provide them with updated road condition information. As one of the drivers is driving to the residential call, he is informed of severe icing along the route. He requests a route change from his ATIS and continues to the residence.

SYSTEM

FUNCTIONAL CHARACTERISTICS

IRANS
IVSAWS
CVO-SPECIFIC

5.3 Pre–drive route and destination selection
5.4 Dynamic route selection
8.2 Road condition information
9.2 Dispatch

 

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.

PURPOSE To illustrate a grouping of functional characteristics from Cluster 1 (5.3, 5.8, 6.3, 6.4, 8.2, 9.1, and 9.2).

SUMMARY A central dispatcher coordinates the progress of 20 separate vans that provide door–to –door airport transportation in one suburban section of a major metropolitan area. Service is provided on demand so that calls are responded to within a specified period of time. If the caller is not picked up within the specified time, the cost of the ride is reduced by 50 percent and a report must be filed by the driver and dispatcher. A dispatcher is also rewarded for making the maximum use of available vans, as determined by the fleet routing system. The dispatcher prepares the first pick–up schedule of the day and transmits this information to the drivers.

SYSTEM

FUNCTIONAL CHARACTERISTICS

IRANS
IMSIS
IVSAWS

5.8 Route scheduling
6.4 Message transfer
9.1 Fleet resource management
9.2 Dispatch

 

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.

PURPOSE To illustrate a grouping of the functional characteristics found in Cluster 2 (5.4, 5.6, 7.1, 7.2, and 8.1).

SUMMARY A young interstate truck operator is traveling at night on a narrow, two–way road. As he is traveling, his IVSAWS provides advance warning of the road closure due to a new construction zone ahead. Because the road closure occurs just prior to a planned refueling stop, the driver uses his ATIS to determine the nearest service station. Having selected one, he requests a dynamic route change to proceed to the station and the help of ISIS to provide speed–limit transitions, street signs, and merge signs.

SYSTEM

FUNCTIONAL CHARACTERISTICS

IRANS
ISIS
IVSAWS

5.4 Dynamic route change
6.2 Services/attractions directory
7.1 Roadway guidance sign information
7.2 Roadway notification sign information
7.3 Roadway regulatory sign information
7.4 CVO road restriction information
8.1 Immediate hazard warning

 

Table 53. Description of Scenario C11.

PURPOSE To illustrate a grouping of functional characteristics from Cluster 3 (5.1, 5.2, 5.7, 9.3, and 9.4).

SUMMARY An experienced interstate truck operator is passing between two States at nighttime. Prior to reaching the inspection point, her WIM system advises her to move to the right–hand lane, where her vehicle is weighed while traveling at normal speeds. Simultaneously, a sensor reads the truck's electronic credentials to validate safety records and debit the trucking company's account for road taxes. Finally, the driver's electronic credential are verified to ensure that her driver's license and permits are up to date and that her operating hours have been within the legal limits. The driver receives notification that all transactions have been performed successfully, and she proceeds at normal speed past the inspection point.

SYSTEM

FUNCTIONAL CHARACTERISTICS

IRANS
CVO–SPECIFIC

5.7 Automatic toll collection
9.3 Regulatory administration
9.4 Regulatory enforcement

 

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.

PURPOSE To illustrate a grouping of functional characteristics from Cluster 5 (6.1, 6.2, 8.4, 8.5, and 8.6).

SUMMARY An interstate truck operator is traveling on the interstate early Sunday morning. As he is driving, his "cargo/vehicle condition monitoring" informs him of a malfunction with one of the trailer's axles. The driver pulls over, checks it, and determines that help is needed. Using the ATIS, he selects a service station that is open at that time and requests their assistance.

SYSTEM

FUNCTIONAL CHARACTERISTICS

IMSIS
IVSAWS

6.2 Services/attractions directory
8.4 Manual aid request
8.6 Cargo/vehicle condition monitoring

 

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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