## 1 Introduction  
Pedestrian safety is one of the main concerns in modern society. Each year, more than 270,000 pedestrians lose their lives on the world's roads, and they constitute two thirds of all road traffic deaths [1]. Despite the reduction of fatalities in European countries in recent years, an increase in fatalities in urban areas has been recorded [2; 3; 4; 5]. As a consequence, traffic engineers and urban planners have increased their focus on vulnerable road users [6; 7; 8; 9; 10]. Accordingly, traffic safety countermeasures have been developed in urban areas to improve the safety of pedestrians and cyclists [11; 12]. The most important factor in pedestrian injuries from vehicle collisions is the impact speed [13; 14]. Therefore, the most frequently adopted countermeasures aim to reduce vehicle speed, to regulate traffic flow within a road section, and to increase drivers' attention. These aspects are important in the actual panorama where the concept of urban walkability is being introduced and the attention paid to pedestrian infrastructures is increasing [15; 16]. Over the years, different systems have been adopted to reduce the risk of vehicle-pedestrian collisions, especially in urban areas. Speed control undulations (SCUs) are traffic-calming units that aim to increase pedestrian safety, as well as reduce noise and pollution from traffic in residential areas. Undulations are usually installed on residential, local, or collector roads; at any rate, these urban roads should not have buses, emergency traffic or, in general, heavy traffic, and should have an administrative speed limit of 20 or 30 km/h [5; 17]. A warning sign with an adequate speed limit sign should be installed before an undulation [1; 18]. When 15% of traffic exceeds the speed limit by 8-16 km/h the enforcement band is not effective [19], and the road manager could evaluate the installation of SCUs and/or other traffic-calming systems. Raised pedestrian crossings (RPCs) are used in urban areas to increase the walkability of neighborhoods [20] and to reduce the probability of pedestrian injuries and fatalities after a crash, either within specific traffic-calming programs, or more generally within Sustainable Urban Mobility Plans, with increased road safety being one of the main priorities in these regulatory tools [21]. The vertical profile of RPCs should comply with dynamic and geometric criteria adopted to designs as a vertical road alignment. In many roads, RPCs are used as SCUs, but this use is only a ploy of the designer or road manager to install a SCU where it is not admitted. In fact, RPCs, unlike SCUs, have no application limits related to road type and are widely used at every type of intersection, and where different traffic functions coexist. A typical example is to locate more bus stops close to raised intersections to enable passengers to minimize travel times and distances while changing lines from one stop to another [22], and thus walk freely across the raised area. RPCs could be more suitable also to mitigate the severity of risks associated with powered two-wheelers (PTWs) when approaching intersections due to fast riding habits, although studies on PTW accidents [23; 24] stress the need to advance knowledge in this field. A broad range of traffic-calming units have been installed in urban areas recently. Vehicle restrictions, warning signs, gateways, speed tables, median islands, channelization islands, speed humps, rumble strips, mini-circles, roundabouts, special pavements and markings, central hatching, warning signs, radar clocked traffic speeds displayed to drivers, lane narrowing, horizontal shifts, and speed control units such as raised pedestrian crossings, speed bumps, or speed humps [5; 25; 26] are the most frequently adopted systems. On the other hand, RPCs encourage drivers to yield to pedestrians: Signed and marked facilities provide a continuous route for pedestrians at the same level as the sidewalk.