  We present a method to automatically calculate time to fixate (TTF) from the
eye-tracker data in subjects with neurological impairment using a driving
simulator. TTF presents the time interval for a person to notice the stimulus
from its first occurrence. Precisely, we measured the time since the children
started to cross the street until the drivers directed their look to the
children. From 108 neurological patients recruited for the study, the analysis
of TTF was performed in 56 patients to assess fit-, unfit-, and
conditionally-fit-to-drive patients. The results showed that the proposed
method based on the YOLO (you only look once) object detector is efficient for
computing TTFs from the eye-tracker data. We obtained discriminative results
for fit-to-drive patients by application of Tukey's honest significant
difference post hoc test (p < 0.01), while no difference was observed between
conditionally-fit and unfit-to-drive groups (p = 0.542). Moreover, we show that
time-to-collision (TTC), initial gaze distance (IGD) from pedestrians, and
speed at the hazard onset did not influence the result, while the only
significant interaction is among fitness, IGD, and TTC on TTF. Obtained TTFs
are also compared with the perception response times (PRT) calculated
independently from eye-tracker data and YOLO. Although we reached statistically
significant results that speak in favor of possible method application for
assessment of fitness to drive, we provide detailed directions for future
driving simulation-based evaluation and propose processing workflow to secure
reliable TTF calculation and its possible application in for example psychology
and neuroscience.
