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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 D. DETAILED TASK ANALYSIS
This section gathers all the private vehicle scenarios and the commercial vehicle scenarios that were chosen as illustrators of particular characteristics for the task analysis. The purpose of this section is to illustrate the task breakdown for each individual scenario, so that it is easier to integrate the nature of the interactions between the ATIS–related tasks and the driving–related tasks.
To facilitate the reader's understanding, this section has been divided into two major portions: (1) all the private vehicle scenarios, and (2) all the commercial vehicle scenarios. For each scenario, the following information is provided: (1) a summary of the scenario's purpose and a brief description of the systems and functions used, (2) a graphical representation of the function interactions, (3) an Operational Sequence Diagram (OSD) of the scenario, and (4) a task breakdown summarizing the driver's activities believed to occur during the scenario.
Assumption. In some of these scenarios, it is assumed that some of the pre–drive activities have already been completed due to the nature of the scenario's environmental conditions. However, the elements pertaining to ATIS may be included if they will be used as part of the scenario's conditions. In addition, in some cases, the scenarios do not describe the driving to destination and, as a consequence, the driving activities have not been included.
Purpose To show the centrality of pre–drive route and destination selection.
Summary A driver is on an extended driving vacation. He has stopped approximately 50 mi (80.5 km) from his destination to review motel options for the evening at his destination point. He accesses the IMSIS directory for the town he will be staying in, reviews several alternative motels, and selects three that are located in one specific area and that look interesting. Before proceeding toward his destination, he makes a reservation using ATIS.
Function Interaction Diagram See figure 29.
Operational Sequence Diagram See figure 30.
Task Characterization See table 55.
Purpose To illustrate a grouping of functional characteristics from Cluster 1 (5.1, 5.2, 5.3, 5.4, 5.6, 7.1, and 8.2).
Summary A driver commutes between her home and the office. The commute requires coordination between three different modes of transportation. She drives the first 10 mi (16.1 km) and then has to decide between taking the ferry across the Bay or driving around the Bay Area. Once she is on the other side of the Bay, she has to drive for another 5 mi (8.0 km) to a park–and–ride lot where she takes a bus to the office. However, she can choose to reject the bus option and drive an additional 10 mi (16.1 km) if the traffic is light. It is a cold winter day and the roads are icy. She needs to get to work in the shortest amount of time possible. She uses her ATIS to plan her trip to the office and to coordinate the travel between the different modes of transportation. After taking the ferry and paying the toll, and while traveling to the bus stop, her ATIS informs her of icy conditions on the road and of bus delays. She selects an alternate route and continues her drive to work.
Function Interaction Diagram See figure 31.
Operational Sequence Diagram See figure 32.
Task Characterization See table 56.
Purpose To illustrate a grouping of the functional characteristics found in Cluster 2 (6.2, 8.1, 8.3, 8.4, and 8.5).
Summary A driver travels on a secondary road where there are numerous speed changes due to the presence of several small towns. As he is driving, the IVSAWS detects a malfunction of the car's brakes. The driver takes notice of the message and continues to his destination. Later on, he receives another message of road construction ahead. The driver applies the brakes, but it is too late; the car collides with a construction vehicle merging from the side of the road. The ATIS activates the aid request to provide assistance to the driver, who is unconscious.
Function Interaction Diagram See figure 33.
Operational Sequence Diagram See figure 34.
Task Characterization See table 57.
Purpose To illustrate a grouping of functional characteristics from Cluster 3 (6.1, 6.3, and 6.4).
Summary A driver uses ATIS to travel from her hotel to a restaurant on the outskirts of town. While traveling, she receives notification that the engine's temperature is increasing. Fearing engine damage, she pulls off the road. The driver then identifies a service station close by. She requests the assistance of a tow truck and cancels her dinner reservation. She also communicates with her friend to inform her of the misadventure with the vehicle and to ask to be picked up at the service station.
Function Interaction Diagram See figure 35.
Operational Sequence Diagram See figure 36.
Task Characterization See table 58.
Purpose To illustrate the sequencing type of interactions among various functional characteristics.
Summary A driver vacationing with his family in an urban setting arrives at the airport in mid–afternoon and rents a car with an IRANS device installed. The family's plan is to go directly to their hotel located in the city 10 mi (16.1 km) from the airport. The weather is good, but there is a substantial level of congestion on the major highways between the airport and the hotel due to normal commuting traffic. After receiving a brief orientation on using IRANS at the rental office, the driver identifies his destination on the IRANS and requests the fastest route. The IRANS recommends a route that the driver accepts and he begins his trip to the hotel.
Function Interaction Diagram See figure 37.
Operational Sequence Diagram See figure 38.
Task Characterization See table 59.
Purpose To illustrate the branching type of interactions among various functional characteristics.
Summary It is Friday afternoon and a driver is following the IRANS guidance in traveling back to her hotel from an appointment with a client. As she drives, she receives the broadcast signal of a nearby winery. She debates between continuing to her hotel or visiting the winery. She uses the ATIS to verify if the winery is open and makes a reservation for the next guided tour. Moments later, she requests a dynamic route change to proceed toward the winery.
Function Interaction Diagram See figure 39.
Operational Sequence Diagram See figure 40.
Task Characterization See table 60.
Purpose To illustrate the interactions among various functional characteristics.
Summary A real estate salesperson is meeting a couple at their residence. She plans on showing them several houses in a suburban area of a major city. She has selected houses in several different neighborhoods spaced around one side of the city. The neighborhoods can be reached by either highways or arterials. It is evening, there is a heavy rain, and there is an accident on one of the highways that could be taken. Two neighborhoods that would be reasonable starting points for the evening's viewing are approximately equidistant from the clients' current residence. The salesperson would like to go to the neighborhood that can be most easily reached first. Prior to picking up her clients, she enters the addresses of all of the houses in the IRANS. During the drive to her clients' house, she monitors the traffic congestion in the planned area of travel. When she arrives at the clients' residence, she requests a comparison of travel times and selects the route that is predicted to take the least time. She then reviews current traffic congestion. Finally, she picks up her clients and drives them to the first house.
Function Interaction Diagram See figure 41.
Operational Sequence Diagram See figure 42.
Task Characterization See table 61.
Purpose To illustrate that the requirements generated by ATIS may impose high workload demands on the driver.Summary A business traveler is driving in the suburbs of a major city that he is not familiar with, during a heavy snowstorm, at dinner time. He has selected a 20≫mi (32.2≫km) drive, recommended by the ATIS, from his hotel to his first destination that is predominantly on arterial roads. In fact, the drive is not a straight line, but rather a series of turns to various arterial roads (no highways). The heavy snow is making visibility poor and the roads icy. He requests that the ATIS provide him with street signs and interchange graphics as well as stop signs and lane≫use control information. Halfway to his destination, he is informed of an accident and of his need to select an alternate route. As he is examining two alternatives, the ATIS warns him of an approaching emergency vehicle. He slows down, pulls over, and enters his route choice. After the emergency vehicle passes, he continues traveling to his destination. Function Interaction Diagram See figure 43. Operational Sequence Diagram See figure 44. Task Characterization See table 62.