Regulatives Fahrerverhalten und dessen Relevanz für das automatisierte Fahren : Ausarbeitung und Untersuchung eines Arbeitsmodells zu funktionalen Verhaltensanpassungen

  • Regulative driver behaviour and its relevance for automated driving : elaboration and investigation of a working model regarding functional behavioural adaptations

Voß, Gudrun Mechthild; Schwalm, Maximilian (Thesis advisor); Müsseler, Jochen (Thesis advisor)

Aachen (2020)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2020


Individual mobility is a central theme of human societies. In this context, the car has become the primary means of transport in which the execution of the driving task already constitutes a high task load for drivers. Nevertheless, they often work on non-driving related tasks. Due to the limited human cognitive resources, this parallel processing of multiple tasks can lead to driver distraction. Yet, people are rarely involved in serious accidents relative to the kilometres driven. Drivers thus seem to have abilities for the avoidance of accidents. Research in the context of non-automated driving can support this claim. Studies could show that drivers - based on their situation awareness - proactively regulate their (cognitive) resources and shift them from the non-driving related tasks to the driving task in case they expect a critical driving situation or driving performance. Various theoretical models dealt with this regulative driver behaviour. Based on these, a holistic working model originates from Schwalm, Voß and Ladwig (2015; Voß & Schwalm, 2015). It conceptualises this regulative driver behaviour as functional behavioural adaptations. While in non-automated driving drivers are responsible for the safe execution and monitoring of the driving task, in automated driving such a permanent involvement in the driving task is no longer necessary, depending on the degree of automation. Drivers can work on non-driving related tasks (from SAE Level 3 on) and drivers’ situation awareness decreases. However, they are allowed to intervene into the automated vehicle guidance at any time or are even required as fall-back option up to a certain degree of automation (until SAE Level 3). This combination of a reduced situation awareness and possible driver interventions in automated driving raises the question of how drivers guarantee a safe driving performance in such situations and whether they can make use of functional behavioural adaptations. This doctoral thesis deals with this topic. The objectives are (a) the theory-based and empirical elaboration of selected components of the working model regarding functional behavioural adaptations from Schwalm et al. (2015; Voß & Schwalm, 2015) as theoretical frame of reference of this doctoral thesis, and (b) the specific investigation of the availability and characteristics of these in the context of automated driving. For this purpose, the working model was detailed theory-based. It was highlighted that the functional behavioural adaptations in the multitasking context particularly occur depending on the perception of a situation and depending on the subjective evaluation of a driving performance. Following, assumptions were made on how functional behavioural adaptations work in the context of automated driving. It was postulated that in case of takeovers, driver proactively reduce activity in non-driving related tasks to release cognitive resources, which subsequently are used for the safe execution of the driving task. These assumptions were empirically assessed. In a driving simulation study (study 1), the functional behavioural adaptations were examined as a function of the perception of a changing driving situation (takeover from automated to non-automated driving). According to the theoretical assumptions, drivers proactively reduced the processing of a non-driving related task before a takeover, released cognitive resources, and thus enabled a safe takeover. The following studies investigated the idea that such functional behavioural adaptations can also occur in case of deviations from a subjectively accepted trajectory. Initially, the construct of a subjectively accepted driving performance was examined by means of discriminant function and factor analysis (study 2). Thresholds of such a subjectively accepted driving performance regarding the lateral offset as a function of various personal and situational factors were examined (studies 3 and 4). Subsequently, studies 5 and 6 investigated the relevance for action of the thresholds in the multitasking context of automated driving in a simulator and under real conditions on a text track. In case the thresholds were exceeded, not only comfort losses but also the expected functional behavioural adaptations occurred. After a proactive reduction of the non-driving related task, drivers often intervened in the automated vehicle guidance. Some of the interventions, however, were not optimal or even safety critical. These insights of the six empirical studies allowed for conclusions regarding the availability of functional behavioural adaptations in the context of automated driving. Furthermore, future research needs were identified, for example a continued working model validation or the design of automated systems which support the functional behavioural adaptations.