**3. Set-up of the simulation scenario**

Sixty-nine young drivers were employed for the driving simulator testing, enrolled on a voluntary basis mainly among the students of the School of Engineering of the University of Florence. Each subject drove the test scenario once. Sixty-one tests were considered valid, whereas the remaining were discarded because of excessive simulator sickness or weird behaviour of drivers and simulator software; the main characteristics of the drivers of valid tests (18 female, 43 male) are shown in **Table 3**. Age varied between 19 and 36 years and also driving experience was very different, ranging from few hundreds of kilometre per year to 50,000. Nineteen tests were actually used to tune the simulation scenario (set-up tests) and, in particular, to synchronise the behaviour of the other road users at the emergency situation. The remaining 42 drivers were used for the actual experimentation.


**Table 3.** Subjects' characteristics.

For the experimentation, the driving simulator available at LaSIS (Laboratory for Road Safety and Accident Reconstruction, University of Florence, Italy) was used. It consists of a full-scale dynamic simulator (**Figure 2**) provided by AutoSIM (Norway, model AS 1200); the complete vehicle cabin and the 200 degrees wide cylindrical screen allow an immersive driving experi‐ ence.

**Figure 2.** View of the simulator in use at LaSIS.

Following the indications obtained from the statistical analysis and the thorough reconstruc‐ tion of typical road accidents, a generic scenario was defined, adapting one of the terrains available in the simulator database. In particular an environment with little population was chosen, in which the emergency situation described above was inserted (**Figure 3**). The driver reaches the point after having driven for about 5 minutes, encountering some vehicular traffic and pedestrians. Since the terrain contains several intersections and roundabouts, to be sure that the drivers reach the point of interest in a given time, indications by means of direction arrows were projected on the screen. The entire test was driven in night time conditions.

**Figure 3.** Map of the emergency situation area.

tests (18 female, 43 male) are shown in **Table 3**. Age varied between 19 and 36 years and also driving experience was very different, ranging from few hundreds of kilometre per year to 50,000. Nineteen tests were actually used to tune the simulation scenario (set-up tests) and, in particular, to synchronise the behaviour of the other road users at the emergency situation.

> **Gender Age km/year Use of lenses** F M Average SD Average SD Yes No

For the experimentation, the driving simulator available at LaSIS (Laboratory for Road Safety and Accident Reconstruction, University of Florence, Italy) was used. It consists of a full-scale dynamic simulator (**Figure 2**) provided by AutoSIM (Norway, model AS 1200); the complete vehicle cabin and the 200 degrees wide cylindrical screen allow an immersive driving experi‐

**Total** 18 43 26.4 2.9 11688 9593 18 43 **Set-up** 5 14 26.6 2.2 10684 7558 3 16 **Tests** 13 29 26.3 3.2 11688 10453 15 27

The remaining 42 drivers were used for the actual experimentation.

**Table 3.** Subjects' characteristics.

88 Autonomous Vehicle

**Figure 2.** View of the simulator in use at LaSIS.

ence.

Before driving the test scenario, the subjects faced a training scenario in which, during about 10 minutes, they could get acquainted with the vehicle cabin and try the most com‐ mon manoeuvres; the subjects began the drive under daylight and ended with dark condi‐ tion in order to get gradually accustomed with night driving. In some of the tests, the presence of an ADAS was simulated, consisting in a pedestrian detection system. Those drivers who were going to drive in the scenario with the ADAS system also experienced it in the training scenario. Before and after the test, each subject was submitted a question‐ naire in order to collect personal and driving information and record their impressions. Be‐ fore the test, the subjects were informed about the aim of the test and were instructed on the basic functions of simulator and cabin; they were invited to drive in a normal way, respect‐ ing the normal traffic rules. No hints were given about the emergency situation they were going to meet. The emergency situation was designed as follows (**Figure 3**): when the inter‐ active vehicle is at a given distance from the emergency area, a vehicle starts travelling in the opposite direction, interfering with the visual. When the interactive vehicle is at a dis‐ tance that corresponds to a time to collision of about 4.5 s, a pedestrian starts walking from 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 4a**).

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

Four different scenarios were set, one without ADAS and three in which the drivers were helped by a simulated PDS assistance system, characterised by different alert modes:

