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The speed is “under control” (at 50 km/h), but still twice as fast as that of the
obstacle (TTC of 4 s and IVT of 2 s). The vehicle going the other way now having
passed, the driver detects the presence of other vehicles and the overtaking
procedure is momentarily abandoned (indicator is reset). The driver then acts on the
break in view of reducing her speed and engaging in a stabilized phase of
monitoring (speed of 20-25 km/h, distance of monitoring the tractor of around 10 m,
and TTC greater than 20 s).
A new overtaking attempt begins 5 s after
View 4
(i.e. she presses on the
accelerator pedal, provoking a TTC fall to 10 s and a slight increase in speed), but it
is abandoned (press on the brake pedal) due to the presence of opposing vehicles. At
the approach of the last vehicle coming the other way, corresponding to
View 5
,
the
driver takes the decision to overtake and anticipates her overtaking action
(activation of the left indicator and pressing of the accelerator). All her attention is
now on the opposing lane (marked lateral offset of the chest and head), in order to
ensure the absence of all other vehicles. In
View 6
overtaking finally occurs (offset
of the vehicle of around 50% at this moment in time): the left indicator is still active,
the steering wheel angle is 48°, and the pressing of the accelerator pedal is 50%,
rapidly causing an increase in the speed of the vehicle.
As in the case presented in Figure 5.2, all the situations of arrival at an obstacle
collected on the open road were subject to a detailed analysis in order to identify the
behavioral and situational markers. This enabled us to propose a model for the
analysis of the driving activity in real time in the form of a “transition-states” graph
(the
states
corresponding to
activity phases
, via the implementation of particular
regulation procedures, and the
transitions
corresponding to conditions required to
pass from one activity phase to the next).
Synthetically, in addition to the initial phase of
driving without an obstacle
(corresponding to
View 1
), this activity model distinguishes four main phases:
- The
risk awareness
phase: corresponding to the detection of an obstacle on the
road and a “break” in the driving situation, thus requiring an appropriate reaction on
the behalf of the driver (
Views 2
and
3
).
- The
regulation
phase: occurring during the approach to the obstacle
in view of
avoiding the collision (i.e. progressive deceleration between
Views 3
and
4
). In the
frame of a critical event, the regulation is based on emergency maneuvers (such as
emergency braking).
- The
stabilized
phase (i.e. situation is under control and the risk of collision is
managed): it can be car-following phase, as is the case in Figure 5.2, or slowing to a
“stationary” position if the obstacle is fixed.
