Stephen Brewster

As autonomous vehicles (AVs) diversify, cyclists may encounter AVs of different sizes. However, existing research on cyclist-AV has mainly focused on passenger cars and has still lacked cross-size exploration. This work conducted two studies to understand how cyclists currently interact with different-sized vehicles, as a starting point for informing how cross-size AVs should communicate with cyclists. Study 1 (survey N=92; focus groups N=8) derived a cyclist-centred four-category conceptual structure of vehicle size (Small, Medium, Large, Huge). Based on this, Study 2 (N=120) asked cyclists to self-report their perceptions and behavioural tendencies when interacting with different-sized vehicles. We found that larger vehicles were associated with lower perceived safety and stronger preferences for spatial distance. These results provide baseline evidence that vehicle size is a potential factor that influences cycling interactions. Therefore, future studies and designs should more explicitly account for vehicle size.

Non-Driving-Related Task (NDRT) interruption has been proposed as a strategy to mitigate control-transition challenges in Level 3 cars. However, it remains unclear whether the system should actively suspend ongoing NDRTs. This paper presents the first study to test empirically whether suspending the NDRT at the moment of a Take-Over Request (TOR) improves takeover performance, hazard perception, and user acceptance across three age cohorts (22–32,60–69,70+) in Level 3 cars. Using a driving simulator, participants responded to TORs during high- or low- mental demand NDRTs, under suspension and non-suspension (active) conditions. Suspension consistently reduced reaction times, yet its benefits were uneven: the largest gains appeared in the 70+ and 22–32 groups. The 60–69 group showed limited benefit in both reaction time and hazard perception, suggesting they retained cognitive flexibility. Suspension increased perceived workload under the high-demand NDRT. These findings establish the benefits and limitations of NDRT suspension and call for adaptive TOR design in future vehicles.

Electrotactile haptics is a novel form of skin stimulation. It is versatile and allows manipulation of many design parameters, broadening the range of haptic experiences. However, how parameter changes influence qualitative experiences is not well understood. We systematically investigated (n = 45) the influence of single parameter changes (e.g., pulse width, frequency), capturing the breadth of experiences elicited. We compared differences between calibration and ordering task performance, first between left and right hands, then between single and both hands simultaneously, all with an open hand and while holding an object, fully exploring the design space. Results showed the wide range of qualitative experience, from concrete to Calibration should be performed on both hands simultaneously to ensure perception, as participants preferred lower pulse width values for simulation on both hands as compared to each hand alone. The results present the first detailed exploration into the qualitative aspects of electrotactile stimulation across the hands.

Conditionally-automated vehicles require drivers to remain hazard-aware while disengaged from driving and engaged in non-driving related tasks (NDRTs), yet conventional visual warning interfaces do not fully address this attentional conflict. While psychological research demonstrates social cues are processed more efficiently than visual information, this has not been evaluated for safety-critical warnings in conditionally-automated driving. This paper presents the first empirical investigation into using a virtual agent to indicate danger and aid situational awareness while driver perform a NDRT. Across two experiments, hazard prediction ability was assessed with either a visual cue or virtual agent cueing danger. When including an attention-capturing element, both visual and social cue types mitigated driver distraction, maintaining hazard prediction comparable with undistracted driving. These findings demonstrate that virtual agents can be as effective as conventional visual cues in aiding situational awareness in safety-critical conditionally-automated driving contexts, offering design insights for in-vehicle attentional displays supporting driver awareness.

Driver eye movements are commonly used as a predictor of visual attention and to estimate situational awareness of a road scene. However, these gaze patterns will change in automated vehicles, where drivers can engage in distracting non-driving related tasks (NDRTs). There is some suggestion that using augmented reality (AR) to present NDRTs at eye-level with the road might be beneficial. This paper evaluates gaze behaviour and situational awareness of experienced drivers (N = 22) while performing an NDRT presented in AR. Eye-tracking data were collected during an experiment where participants were simultaneously performing a Hazard Prediction task and an AR keypad dialling task, presented either as a Heads-Up Display (HUD) or Heads-Down Display (HDD). The results suggest that eye movements were significantly affected when engaged with an NDRT, resulting in an impaired ability to predict hazards. This was also evident even when attention was explicitly cued towards the area of the road where a hazardous event was occurring. The results from this study indicate that driver fixations alone do not suggest they have situational awareness, in particular when interacting with a distracting NDRT. From this, we provide considerations for designing AR interfaces to be displayed to drivers of conditionally automated vehicles.