**2. Definition of a reference accident scenario**

require political decisions and a proper legislation will most probably be necessary, for instance as regards the realisation of the needed infrastructures and the settlement of issues related to legal liability. This last point can be particularly important: who will be responsible when an accident happens, as certainly will? It can be imagined that the involvement of car manufacturers and their suppliers will be greater, in a context that will also involve insurance companies, governments and customers [9–11]. User acceptance will play a fundamental role; in reference [12], for instance, a worldwide survey was carried out in order to understand how autonomous vehicles will be accepted, comparing all levels of automation (from conventional driving to full automation). In this study, the major concerns of future customers were indicated, including legal issues, cost (22% declared themselves unwilling to pay any addi‐ tional sum for an automated vehicle), security (regarding especially software being subject to hacking), privacy concerns (vehicles are subject to be constantly monitored) and driving pleasantness, etc. Geographical differences were also pointed out. In reference [13], the intention of French drivers to use a partially or fully automated vehicle was investigated. In reference [14], the possible effect of motion sickness on user acceptance is investigated, and the necessity of considering such issue during the design and development phase is emphas‐ ised. Thus, if a fast and successful introduction in the global market is desired, such systems must be implemented in such a way as aiming at high performance and high user acceptance, and such steps require the most complete understanding of driving behaviour: in other words,

In the initial phase of the development of ADAS, it is a common practice to carry out testing in controlled environment, namely, by staged driving sessions or using driving simulators. Since their introduction, driving simulators have been widely used to study safety and human factor-related issues. Since the first appearance of advanced driving simulators they were extensively used to investigate over safety issues [15, 16] and also as an important tool in the

**–** Situations that normally reveal to be dangerous can be faced without any risk for the driver

**–** A well-designed testing scenario allows a very good repeatability of the driving environ‐ ment and control of all variables (traffic, course, road and weather condition, etc.).

**–** The situations through which the driver goes can be adapted to the driver behaviour itself.

On the other hand, the driving scenario must be carefully designed in order to obtain a sufficient representativeness of the results, and often a validation activity must be carried out, for instance by carrying out staged tests in controlled environments or by monitoring real-life driving. Moreover, not all the drivers are able to drive comfortably in a driving simulator.

**–** All testing parameters can be easily recorded and stored for successive elaboration.

a driver model (or better, driver models) must be set up.

The use of simulators presents numerous advantages:

and for the researchers as well.

**–** Experimentation can be speeded up.

design and assessment of advanced driving assistance systems [17, 18].

**1.3. The role of simulation**

86 Autonomous Vehicle

Among road users pedestrians represent one of the weaker categories, and the percentage of accidents involving pedestrians is relatively high. According to WHO [19], in 2013, 22% of about 1.25 million worldwide road traffic deaths were pedestrians. In the USA, during 2012, 4743 pedestrians were killed (total casualties 33,561) and 76,000 were injured (total 2,362,000) [20]. It can be seen that the percentage of deaths with respect to injuries among pedestrians (6.2%) is much higher than the general one (1.4%), thus confirming the high level of danger. Pedestrian safety is expected to be highly boosted by the adoption of assistance systems as pedestrian detection system (PDS) and V2I communications, and for this reason it was chosen to study the drivers' behaviour in a situation with a high risk of being involved in an accident with a pedestrian.

Accident reconstruction is a powerful tool to explain the reasons of an accident and identify the main contributing factors. Thus, 26 accidents involving pedestrians actually happened in Austria were analysed using the CEDATU (Central Database for In-depth Accident Study) database [21, 22], by also using multi-body simulations (PC-Crash, DSD, 2015).

Following the indications collected during the preceding phase, a reference accident scenario was defined having, among others, the following features: low-density population urban environment, late evening (heavy darkness) with scarce electric lighting, good weather and road conditions, non-intersection, and pedestrian not using a crosswalk and walking without running from left to right; moreover, a car is coming from the opposite direction obstructing the visual.
