Article Preview
TopIntroduction
Self-driving vehicles represent a potentially disruptive and beneficial change to the way in which we travel. This new technology has the potential to increase safety on public roads, decrease traffic congestion and enhance driver satisfaction (Anderson et al., 2014). Thus, it is not surprising that leading automotive makers and major corporations have been announcing plans to introduce self-driving vehicles in the next decade (Litman, 2014). However, despite promising technological breakthroughs in the field of automated driving, the reliability of these technologies still largely depends on external conditions such as the road type, weather and daylight conditions. It is therefore likely that in the near future vehicles will only have limited self-driving capabilities. In semi-automated vehicles, the vehicle will be in full control of the driving task only under certain traffic and environmental conditions, otherwise the driver is expected to be in control of the driving task. According to NHTSA (2013) and SAE (2014) levels of automations definitions, conditionally-automated driving (level 3 automation) is a setting in which drivers rely on the vehicle to monitor for changes that will require them to regain control. The driver is still expected to be available for occasional control during automated mode, and must be prepared to resume full responsibility for driving within an acceptable amount of time.
The requirement to prepare the driver for the handover of control raises a number of key issues. Previous studies found that drivers' awareness of surrounding traffic is relatively low in automated driving situations because they allocate less attention to the road and more attention to other tasks which are non-driving related such as watching movies or texting (Llaneras, Salinger & Green, 2013; Carsten et al., 2012). In the aviation domain, a similar phenomenon, termed automation complacency, has also been reported in studies examining vigilance and monitoring in automated aviation environments. Automation complacency refers to the finding that flight crews tend to rely fully on the automated system for flight tasks and pay less than sufficient attention to monitoring these tasks (Parasuraman, Molloy & Singh, 1993; Parasuraman & Manzey, 2010). The implication is that drivers' responses will be delayed and insufficient when requested to resume control, since they will have to scan the entire traffic environment before making an appropriate action.
The current study tested a solution to increase driver awareness to surrounding traffic during automated driving. We examined a system that projects continuous information about the relative spatial position of approaching vehicles onto a vibrotactile display embedded in the back of the driver's seat. We predicted that when drivers would be asked to regain control of the vehicle they would do so more quickly and efficiently since they would already have a high level of awareness of vehicles in their surroundings. The focus on the haptic modality is based on a growing body of literature that has established the potential advantages of providing driving-related information via the haptic modality (Petermeijer, de Winter & Bengler, 2015). Several studies have examined the usefulness of vibrotactile interfaces as a way to project spatial and temporal information. These studies have found that vibrotactile displays consisting of a number of vibrating elements are quite effective and intuitive in terms of presenting directional information such as sequence and location (Tan et al., 2003; Van Erp & Van Veen, 2004). Van Erp and Van Veen (2001) presented navigation directions such as right turn and left turn to drivers either as a visual display or a vibrotactile seat display. The participants reported lower levels of cognitive workload and exhibited better response times for the vibrotactile navigation display than without it. Terrence, Brill and Gilson (2005) examined the effect of alert modality on the participants’ ability to localize alerts. The results indicated that tactile feedback robustly improved both localization accuracy and reaction time as compared to the auditory modality.