Is It Possible Or Not? Situation Awareness In Using Secondary Tasks While Driving

摘要

Am Beispiel der Bearbeitung von Nebenaufgaben während der Fahrt wird ein Arbeitsmodell des Situationsbewusstseins entwickelt und überprüft. In einer Versuchsanordnung in der Fahrsimulation wurden den Fahrern in unterschiedlich anspruchsvollen Situationen Angebote zur Bearbeitung einer Nebenaufgabe gegeben. Sie konnten jeweils entscheiden, ob und wie lange sie sich in der aktuellen Situation mit dieser beschäftigen wollten. Die Entscheidungen der Fahrer im Umgang mit der Nebenaufgabe ermöglichen es, relevante Aspekte von Situationsbewusstsein, wie antizipative Prozesse der Handlungsplanung als auch kontrollierende Prozesse der Handlungsabsicherung, zu identifizieren.%The concept of Situation Awareness was originally developed in aviation but has also become more and more important in the domain of driving. Endsley (1988) defines Situation Awareness as "the perception of the elements in the environment within a volume of time and space, the comprehension of their meaning and the projection of their status in the near future" (p. 792). In her model she argues that a cognitive representation (schema) of the current and the future situation is formed on the base of knowledge in long-term memory which guides attention to the relevant cues in the environment. Due to the dynamics of the situation, this mental representation has to be continuously updated. This update is understood as a cyclical process, including an active search in the environment for information which may prove or disprove the activated schema and lead to modifications. In this report a secondary task method is presented to investigate Situation Awareness in the driving context. It is assumed, that the self paced use of secondary tasks can be used as an indicator for drivers' Situation Awareness. Situationally aware drivers are able to decide in accordance with the demands of the actual driving situation if execution of a secondary task is safely possible or not. This enables them to avoid higher workload levels in already demanding driving situations. Maintaining Situation Awareness when using secondary tasks includes anticipative processes based on accurate perception and comprehension of the situation just before a secondary task is started as well as continuous updates of the situation model via control processes during secondary task execution. To investigate these processes, a study in the driving simulation was conducted. The driving course consisted of specific situations, each including a potential conflict. In every situation, the driver had to adapt his driving behaviour appropriately to ensure driving safety. In addition, situations without any special demands on the driver were constructed. At predetermined points of the route, the driver was offered the choice to perform an additional task. This offer was given either just before a critical situation or in a non-critical situation. Given such an offer, the driver had to decide within a given time frame whether the situation was suitable for the secondary task or not. This should be done according to the situational demands. The driving task should always remain the primary task. In study 1, a highly standardised, externally paced task was implemented. It consisted of sequentially displayed numbers with a fixed duration of 500 ms per number. The driver was told to read each number aloud just after it had appeared on the display. The driver was instructed to perform the task for as long as the situation allowed (maximum 5 sec). He was instructed to interrupt the secondary task and return to the driving task whenever the driving task required full attention. If the task had once been interrupted, it could not be continued. In study 2, a realistic menu system was implemented. This task was self-paced by the driver and could be interrupted any time. The task was to navigate to instructed options within the menu. In both studies, behavioural adaptations in the driving task, in the secondary task as well as in the allocation of visual attention were measured. To evaluate the adequacy of these strategies, the effects on driving safety were analysed (driving errors and collisions). The results of both studies show that our experimental setting allows the use of situationally adaptive strategies in the interaction with secondary tasks while driving as an indicator of drivers' Situation Awareness. Indicators for anticipative as well as control processes could be found: In anticipation of higher future situational demands, drivers rejected tasks more often to avoid overload due to the dual task situation. Furthermore, drivers interrupted task execution timely before a critica