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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
CHAPTER 4. TASK ANALYSIS RESULTS
Analysis of Tasks Integrated with Critical Driving Functions
The value and usefulness of the ATIS are found largely in the driving environment. An understanding of the interaction of ATIS/CVO tasks with the primary tasks associated with driving during critical periods is an important factor in the development of human factors design guidelines for ATIS.
Function of Tasks Integrated with Critical Driving Functions
Tasks associated with ATIS/CVO use include some that must take place in close proximity to driving tasks, such as scanning for pedestrians or obstacles, controlling the vehicle in speed and direction, and coordinating the position of the vehicle in relation to other vehicles on the road. Such tasks are of particular importance to an understanding of the design requirements necessary for ATIS/CVO systems to be used safely on the road. Examples of such tasks include:
General Characteristics of ATIS Tasks Integrated with Critical Driving Functions
Of the 165 driver or dispatch–centered tasks examined in detail, approximately 13 percent directly involved the integration of ATIS/CVO system tasks with driving. This should not be construed in any way as an indication of the likely distribution of the various tasks that would be encountered in operational systems. Such a distribution will obviously depend on the specific design of the system and how drivers actually use it.
Although ATIS may provide information to drivers that is of interest, the real importance of ATIS use is found in the execution of the ATIS recommendations on driving behavior. In the scenarios evaluated as part of the task analysis, tasks that integrate ATIS functions with driving functions are based on two different types of requirements:
Tasks that integrate the results from the IRANS route guidance tasks with driving behavior lead to the driver maneuvering the vehicle to follow a planned route (see figure 23; also see appendix D, Scenarios P1 OSD, P2 OSD, P16 OSD, P20 OSD, and C12 OSD). Such tasks are preceded by a decision task that determines that the recommended action is safe and appropriate; they are usually followed by a resumption of the ATIS tasks.
Tasks that integrate the results of ISIS and IVSAWS notification and warning tasks with driving behavior result in the driver taking action based on experience and training (see figure 24; also see appendix D, Scenarios P8 OSD, P14 OSD, P22 OSD, C4 OSD, C11 OSD, and C15 OSD). Such tasks are preceded by a decision that the notification or hazard requires immediate action, and they are usually followed by modification of the planned trip.
For ease of understanding, these two sets of functions for tasks integrated with critical driving functions have been summarized in table 22.
Table 22. Summary of tasks integrated with critical driving functions.
Human Factors Design Implications (General and Specific)
In the sequence of actions involving ATIS tasks integrated with critical driving functions, ATIS initially informs the driver of a recommendation or provides warnings or notifications of an event. In order for the recommendation or notification to be effective, it is essential that the driver be able to receive and process this information.
Upon receiving and processing this information, the driver must make a decision. This decision task must determine whether an immediate action is needed or not, or in other instances, whether the ATIS–recommended action is safe and appropriate.
Upon deciding what action to take, the driver must proceed with his or her driving tasks. Tasks that integrate ATIS functions with driving are basically vehicle control tasks. As such, when the decision has been made to execute the tasks, they both become the primary focus of the driver's attention and are within the normal range of driver performance.
Table 23 summarizes the general characteristics and considerations associated with integration tasks that involve both driving and ATIS use.
Table 23. Summary of the general characteristics and considerations associated with integration tasks that involve both driving and ATIS use.