Takahiro Matsuoka, Tsuyoshi Nojiri, Vanessa Krüger, Matti Krüger, "Novel interfaces that enhance a driver’s ability to perceive forward collision risks", 27th International Technical Conference on the Enhanced Safety of Vehicles (ESV), 2023.

Forward Collision Warning (FCW) systems that alert a driver about the risk of rear-end collisions can contribute to a reduction of traffic accidents caused by human errors. Typically, FCWs create alerts that appear late when the risk is already high and are of binary nature, i.e., either in an alerting state during high risk or not producing any alert at lower risks. The choice at what risk level to start alerting in a binary manner is subject to a tradeoff between how much time an alert gives the driver to react and how necessary the alert appears to the driver. Our goal is to circumvent this limitation of classical binary FCWs to allow drivers to perceive developing risks early and in an intuitive manner and, accordingly, better avert developing risks with foresight. To that end, we propose a new system that assesses potentially hazardous situations in real time and continuously outputs a signal that alters its strength depending on the risk level. Here we report a study on the effect of variations of the proposed system on driving behavior and user acceptance. The experiment was carried out in a driving simulator equipped with prototypes of visual, auditory, and tactile human-machine interfaces (HMIs). The participants performed driving tasks in two different driving scenarios. The subjective ratings of system acceptance were assessed with questionnaires on two dimensions, a usefulness scale and an affective satisfaction scale. The results indicate that, compared to an existing FCW system, all HMIs reduced driver reaction times and the visual HMI showed positive average scores of both usefulness and satisfaction in the driving scenario with high and medium collision risk. On the other hand, there was no HMI that achieved a good balance between the effect on driving safety and system acceptance in the scenario with lower criticality. These results suggest that the proposed notification system can improve driving safety and be perceived as subjectively acceptable in situations with high and medium collision risk despite the early signal. This makes it a promising approach for circumventing the tradeoff between notification timing and risk perception. To address system effects on driving safety in situations with lower risk, further development iterations and long-term evaluations in a variety of traffic situations may be required.