With the increase of electric vehicles on the roads, there is also an increase
with vehicles that use regenerative braking (RB). This novel braking method
differs from traditional service braking (SB) because RB decelerates the moment
the driver releases the accelerator pedal and continues to actively brake if
neither pedal is depressed. Since the vehicle actively decelerates when neither
pedal is depressed in a vehicle with RB, we hypothesized that this would result
in a difference in driver foot behavior. There were two pieces to explore this
potential difference.
The first piece was to explore time-based measures. The first measure was the
time period from when the lead vehicle brake lights illuminate, to when the
driver releases the accelerator pedal. The second measure was the time period
from when the driver releases the accelerator pedal, to when the driver presses
the brake pedal. When comparing RB and SB, there was no statistically
significant difference for the first time-based measure. When comparing RB and
SB for the second time-based measure, the high level of RB was statistically
significantly different.
The second piece was to code each video to label driver foot behavior based on a
set of categories. The 5th category (uncertainty − “wagging foot”) was the only
foot behavior appearing in all three conditions (n = 2, SB; n = 4, low RB; n =
6, high RB). The 8th category (brake tap, reposition to throttle, then brake
press), only appeared in the high level of RB condition and appeared 9 times
(33% rate).
This study shows that RB results in differences in driver foot behavior when
compared to SB in the time period between accelerator release and brake press.
It also shows that RB results in drivers engaging in foot behavior indicating
uncertainty.
