NEW APPROACHES TO EVALUATE THE SUSTAINABILITY OF URBAN TRANSPORT INFRASTRUCTURES

The advent of the new concept of mobility, understood as sustainable and intelligent, has led to the growth and development of new forms of transport, especially in micro-mobility. Cyclists, scooter drivers, and pedestrians are becoming predominant categories within contemporary urban travel. However, if on the one hand, the evolution of the concept of urban transport certainly leads to environmental benefits such as the reduction of pollution, congestion, and so on, on the other hand, it brings with it a series of non-negligible problems. Statistical data from national, European, and international bodies underline that users of these means of transport, called vulnerable road users (VRUs), are the category most at risk of accidents. This is mainly because current transport infrastructures cannot securely accommodate such users. This PhD thesis deals with the issue of the safety of vulnerable road users in a multidisciplinary way, first investigating the exposure to which these users are subjected in their movements, then analyzing their relative vulnerability, and finally verifying the effectiveness of countermeasures to be adopted to reduce the risk they incur. Specifically, the thesis is structured as follows: - Introduction: The issue of sustainable mobility is addressed, referring to the main regulatory acts that regulate it, such as the 2030 Agenda. Descriptive statistics are introduced, highlighting the current safety problems of vulnerable road users. Finally, the main objectives that this research aims to achieve are described. - Chapter 2: The first risk factor, i.e., exposure, is addressed. The intention is to investigate pedestrian crowding, first by developing a hybrid configurational model and then calibrating and validating it with experimental data. Regarding the configurational model, ad hoc parameters have been weighted to make the model as close as possible to reality. Regarding the experimental side, a virtual data collection methodology has been developed using open source tools such as Google Street View. Furthermore, to improve the accuracy of this methodology, Python software has been designed for pedestrian recognition from video recordings, to capture daily and seasonal variability, which is undefinable by Google Street View. - Chapter 3: The aspect of vulnerability is investigated by studying the impacts on vulnerable road users. A focus is made on the interaction between pedestrians and scooter riders, reconstructing the impact dynamics using Virtual Crash software. The Head Injury Criterion (HIC) is used to describe the injuries suffered by users as a result of the impact. This research aims to identify a physical model that can tell the impact dynamics well and allows for investigating the extent of the injury suffered by users without resorting to complicated software, such as the Virtual Crash, but knowing only the pre-impact quantities. In this regard, Python software has been developed to evaluate both users' HIC, inserting only pre-impact amounts into it. - Chapter 4: This chapter analyses the role of the countermeasures to reduce the risk these users incur during their travels. Among the possible countermeasures, traffic calming devices are analyzed, evaluating their effectiveness. In particular, attention is given to the role of the vehicle fleet in its performance. The thesis, in particular, aims to examine the influence of the vehicle category on the speed reduction recorded as vehicles pass these devices. If this were true, it would be necessary to consider, in the design phase, the types of cars that will affect the road on which the speed bump will be installed, to have a desired speed reduction. A theoretical model is first developed, based on the mathematical model of vehicle-half-car infrastructure interaction, then calibrated and validated thanks to experimental data collection. This data is collected in two ways: video footage and recordings via on-board dataloggers. In addition, creating a real driving scenario to be inserted into a driving simulator in Katowice, Poland, where data can be obtained to validate the developed theoretical model, has begun to be implemented. It is also intended to define a calibration coefficient that allows for determining the shift between real and simulated data, making it possible to easily design various calming traffic devices within the driving simulator environment. - Chapter 5: The results obtained in this thesis are analyzed, and their future developments are defined.