While an enlarged lead time from risk notifications to collisions is widely
acknowledged to facilitate safe driving, it remains challenging to effectively
notify drivers of invisible risks and non-apparent risks coming from uncertain
behaviors on the part of road users. The current study examined whether verbal
notifications are able to assist early awareness of predictive risks. We also
attempted to identify human and environmental factors that could possibly
improve the effectiveness of predictive risk information.
Twenty-eight licensed drivers participated in a public road test conducted in two
different urban areas on 3 days. They drove predefined courses on which
potential risk locations were identified prior to the test, using a sport
utility vehicle equipped with an automatic verbal notification system triggered
based on the distance to the potential risk locations. After passing through the
locations each time, the participants were instructed to verbally evaluate the
shift in awareness provided by the notification and the usefulness of the
assistance. After the driving test was completed, we acquired a subjective
evaluation on annoyance acceptability and a self-report of participants’ road
usage frequency at notified locations in daily life, as well as questionnaires
on their driving style and workload sensitivity. We found that the effectiveness
of verbal notifications increased by conveying uncertainty risks at visible
locations and by using interrogative sentences or expressions of risk target
perspective, although it decreased as a function of age. Our model showed strong
performance in predicting positive ratings for the notifications, but this was
not the case for negative ratings. We identified individual characteristics and
the risk factor of uncertainty as important features in our model.
In conclusion, the findings provide an important reference for understanding the
early notification of predictive risk and constructing a numerical model for the
implementation of assistance systems in vehicles and nomadic devices.
