**4. Data analysis**

To obtain the results, data from three sources were analysed:


From such data, besides a qualitative description of the driver's behaviour, the following values were calculated:


$$ADE = \frac{V}{2 \cdot (ttc - t\_k)} \tag{1}$$

In the present study, when *ttc* refers to the moment of braking onset, *tR* is put equal to zero.

#### **5. Results**

the opposite side of the road, heading along an oblique direction, with a constant speed of 1.67 m/s; in the first part of his path, the pedestrian is hidden by the distraction vehicle

**Figure 4.** Scene of the emergency situation as seen by the subject driver: in scenarios A, B and C (a) and in scenario D

Four different scenarios were set, one without ADAS and three in which the drivers were

**–** Scenario B: a sound alarm (consisting of beeps with increasing frequency) is issued after 0.5

**–** Scenario D: as scenario C (10 drivers) with the addition of a visual warning, consisting in a self-lighted rectangular frame around the pedestrian (**Figure 4b**). The aim was to provide additional information to the driver about the position of the hazardous situation, simulat‐

**–** Disk recording of several parameter of the vehicle, at the rate of 20 S/s, including position, speed, acceleration, pedals use, gear, steering wheel position, vehicle position in the lane,

From such data, besides a qualitative description of the driver's behaviour, the following

**–** Visual recording of the entire simulation, as performed by the simulator software.

helped by a simulated PDS assistance system, characterised by different alert modes:

**–** Scenario C: as scenario B except that the sound is emitted after 1.5 s (10 drivers);

**–** Scenario A: no ADAS was simulated (12 drivers);

To obtain the results, data from three sources were analysed:

**–** Information filled in questionnaires by the subjects.

s the pedestrian start (10 drivers);

ing the use of a head-up display.

**4. Data analysis**

values were calculated:

etc.

(**Figure 4a**).

90 Autonomous Vehicle

(b).

All of the subjects had some reaction when approaching the pedestrian, but only 29 drivers out of 42 succeeded in carrying out a successful manoeuvre to avoid the collision. Usually, the drivers reacted by releasing the accelerator pedal and pressing the brake pedal; only two out of 29 successful drivers, after a short use of brakes, steered and avoided the obstacle (tests 31 and 34). None of the drivers chose to steer instead of braking. Thirteen drivers out of 42 hit the pedestrian (see **Table 4**): 50% in scenario A (without ADAS) and 23% in all the scenarios with ADAS. Of these only 4 out of 13 tried, while braking, to steer.


**Table 4.** Number of failed and successful tests in different scenarios.

Tests without ADAS had higher speed at collision than those with ADAS, being in average 33.1 km/h (SD = 11.9 km/h) versus 22.4 km/h (SD = 9.4 km/h), with some statistical significance (*P*-value = 0.06 following the *t*-test [23]). As regards the functions of the simulated ADAS device, 4 out of 30 declared they did not hear the acoustic alarm, whereas 10 out of 10 saw the visual one.
