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Federal Highway Administration Research and Technology
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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 Setup Tasks Tasks that are used to provide information to the ATIS were the first types of tasks analyzed. An understanding of such tasks is essential to the development of appropriate driver input devices and approaches. Function of Setup Tasks Input tasks are generally defined as tasks that have the purpose to gather and provide information needed by an ATIS to begin or complete necessary processing. Examples of various setup tasks include:
Setup tasks appear to perform four different functions related to the use of ATIS/CVO systems. These four different functions are summarized in table 16. Table 16. Function and description of setup tasks.
For this analysis, setup tasks were limited to tasks performed by a driver or dispatcher to initiate system functional operation, to provide goal–related information (e.g., destination location), or to limit considerations of the system. General Characteristics of Setup Tasks Of the 165 driver and dispatch–centered tasks examined in detail (see appendix D), approximately 42 percent were tasks associated with setting up an ATIS/CVO system. Setup tasks involve both cognitive and motor activities that need to be considered in connection with the likelihood of good task performance. Since setup tasks involve several different types of activities and perform different functions in the use of ATIS/CVO, they may involve different performance considerations. The tasks associated with turning the system on or preparing the system to perform a design function (see figure 10) are likely to be among the least demanding tasks associated with the use of ATIS, particularly since many of the setup initiation tasks would be performed during the pre–drive phase of a trip. One notable exception to this would be when a driver executes a dynamic route change (see appendix D, Scenarios P20 OSD, C4 OSD, and C12 OSD). In such circumstances, the setup is usually performed in conjunction with a series of decision–making actions and may often be performed while driving.
Setup tasks that are critical to performing a function (see figure 11) usually involve complex cognitive and relatively complicated motor processes. Representative of these types of setup tasks are those that involve identifying and entering a destination. This type of information often involves a complicated series of steps that depend on the driver's long–term memory and knowledge of specific information about the destination (i.e., street address, town name, or cross–street).
In addition to the task elements of collecting the information required by the system, the setup task also involves entering the information. Assuming that the destination includes a normal address, the detailed entry process likely to be required when performing a setup task of a flexible destination indicates that workload and attention requirements of the task might preclude it being done while moving. Aside from setup tasks involving flexible destinations, it would also be possible to have the system pre–programmed for destinations that are frequently used (e.g., work, home, and selected destinations frequently used). Such destinations would allow the driver to select them from a limited destination menu when setting up IRANS systems and thus eliminate much of the normal destination setup activities (see appendix D, Scenario P14 OSD). The same would also be true of the entry of pre–programmed destinations that might be obtained from technologies such as address bar coding on newspaper advertisements or business cards. In addition to flexible destination setup tasks used with IRANS, there are setup tasks associated with cataloged destinations such as public buildings, businesses, and significant landmarks (see appendix D, Scenarios P6 OSD, P16 OSD, C4 OSD, and C15 OSD) that could be accessed via multiple menu windows (see figure 12). While a menu–driven sequence does not require the same degree of cognitive preparation and information–entry expertise that is required to set up a flexible destination, the tasks involved do include the necessity that the driver focus a great deal of attention on the ATIS equipment and are thus likely to be incompatible with the primary task of driving.
The task of entering parameter information for driver or dispatcher preferences for how an IRANS will perform a planning function, will most likely use a menu–driven approach, due to the limited number of parameters that are likely to be important for a particular function. These types of functions (see figure 13) may also be suitable for automatic or semi–automatic settings depending on driver preferences, vehicle design, and other conditions that would automatically set the system up and, therefore, would be transparent to the driver.
The last type of setup task is made up of those tasks that are used to confirm that the system is correctly set up (see figure 14). These tasks would usually involve a review of the input provided or the recommendations developed from that input. The method for presenting this information may be quite complex and detailed. In these instances, the complicated review tasks probably would preclude their being performed while also performing the primary task of driving.
Human Factors Design Implications (General and Specific) Human factors design implications, be they general or specific, will depend on the purpose or actual function of the system. For the setup tasks, there were four different types of functions identified. For each one of these functions, there might be different human factors design implications. The following paragraphs summarize these design implications for each one of the setup tasks. First of all, the primary task performance characteristics for turning on or initiating the ATIS are likely to be that the controls required are within easy reach of the driver, are large enough to be easily controlled, and provide positive feedback to the driver that the system or function has been initiated (see appendix D, Scenario P20 TC). Representative of these types of setup tasks are those that involve identifying and entering a destination. This type of information often involves a complicated series of steps that depend on the driver knowing specific information about the destination (i.e., street address, town name, or cross–street). The attributes of such information may depend a good deal on the size of the map data base used by the system, as well as the nature of political and geographic divisions in a particular part of the country. The first and perhaps most important characteristic of this type of setup task is that it requires the driver or dispatcher to have an accurate and precise description of the destination that is also compatible with the data base used by the system. Therefore, system design needs to be consistent with the most likely way that people identify the locations they drive to. For example, street mailing addresses are probably more useful for ATIS systems than some other destination reference system would be (e.g., latitude and longitude or Universal Traverse Mercader [UTM]). Aside from the problem of having the proper information to correctly specify a destination, the driver must also correctly communicate this information to the ATIS. This task can obviously be done in a variety of different ways. For example, a destination address may be entered using either a keyboard, touch screen menu, or some combination of the two. Assuming that the destination includes a normal address, the entry must provide the system with both numerical and alphabetical information in a series that is likely to exceed 20 to 30 characters. This implies the necessity for an entry device that:
Other alternatives to data entry techniques include having an abbreviated menu of pre–planned destinations (e.g., office, home, and frequently visited friends). Use of a pre–planned personal destination menu would greatly simplify the setup task for those destinations. Other means of entering individual destinations might include the use of programmed "smart cards" that would allow planning a series of destinations prior to beginning a trip. Perhaps the most obvious use of such "smart cards" would be for commercial applications, such as small package delivery, where a support system could be set up to prepare the card. The task performance considerations associated with setting up destinations from cataloged information, such as might be available from IMSIS, vary slightly from those needed for entering non–cataloged information. Such a task would almost certainly be based on using a hierarchically organized menu–driven system to arrive at a listing of alternative services and then to select the desired alternative from that list. The first performance characteristic that is likely to be associated with such actions is going to depend on the user's knowledge of the structure of the categories used by the system and the ability to correctly place the desired destination or class of services within the appropriate category. Efficient use of the directory will depend in large part on the knowledge that the user has of the categories used by the system. This could, of course, be improved by the development of a standardized taxonomy of services presented in the ATIS. Aside from needing to know the structure of data base categorization, performance will depend on the ability of a driver to recognize an appropriate match between the requirements that they have for services and the services listed in the menu. In most cases, this ability will be dependent on the type of services needed and the number of options available (e.g., a driver will have less difficulty selecting post offices than Chinese restaurants). The tasks associated with establishing parameters for system use are similar to those required for all menu–driven systems, with the exception that these parameters are likely to represent a smaller set of choices than the driver can make. Finally, the task of confirming proper system operation is likely to involve much more than simply verifying the mimic of the information needed to be entered, but also, the much more complex process of determining if the system recommendations are reasonable and appropriate for the circumstances. This involves not only verifying that the information was correctly entered in the system, but also that the information was correct at its inception. Such checking also involves making a determination that the basic information the system uses (i.e., the data base and the computational assumptions) is correct and appropriate. This type of verification involves the user in a combination of cognitive activities that include the use of previous experience, knowledge, and the assessment of multiple sources of information that might have a bearing on the outcome of a particular recommendation. Finally, since it can be assumed that many destination entry tasks will involve, at least partially, the use of long–term memory, an ATIS might also include intelligent evaluation of destination input that would provide logical as well as direct matching of the driver's input with the data base. For example, if a driver enters an address that does not exist in the data base for a specific area, the system might respond with suggestions of possibly correct alternatives in a manner similar to that used by spell check features used in word–processing programs. Table 17 summarizes the general characteristics and considerations associated with setup tasks. Table 17. Summary of the general characteristics and considerations associated with setup tasks.
Return to Task Analysis Results
FHWA-RD-95-176
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