## 3 Results  
This study is based on the results of surveys carried out on RPCs in Italian urban areas (Figure 4). Twenty four two-way roads with RPCs were considered (each observed RPC is named as \"site N\", where N ranges between 1 and 24; when two directions have been measured, the letters \"a\" and \"b\" are added after the ID \"site N\"). The campaign consisted of visual surveys, measurements of the RPC's geometrical characteristics, and measurement of the effective speed of vehicles passing along the RPC. Table 2 summarizes the results of the visual surveys. It highlights that pavement depressions before RPCs and localized damages on RPCs are 21% and 34% of the survey sample, respectively. For all the surveyed RPCs vertical signs were present, while only 17% had horizontal markings on the RPC; 12% of sites did not have horizontal markings after ramps. Figure 5 shows the most frequently observed distresses and damages on the road pavement: Depressions on the access ramp (Figure 5a) or after the exit ramp (Figure 5b), and grooves on the pedestrian crossing surface (Figure 5c) or after (Figure 5d) the RPC, which indicate vehicle-pavement contact. Figure 6 shows the RPC longitudinal profile obtained from Dipstick for two surveyed RPCs (i.e., site 1b and site 17 in Figure 6a,b, respectively) where the administrative speed limit is 40 km/h. Both curves describe the pavement profile along the centerline of each RPC. During the surveys, the self-made device measured the effective speed of vehicles through each RPC: Figure 7a,c represent the relative speed distributions measured at the half speed table points of site 1b and site 17 (i.e., profiles in Figure 6a,b) respectively. Although the speed distribution is discrete, the Gaussian curve can fit the experimental values: Figure 7b,d refer to the relative speed distributions in Figure 6a,c, respectively. The results in Figure 7 highlight that about 14% and 7% of drivers passing through site 1b and 17, respectively, do not respect the speed limit (i.e., 40 km/h). Given the longitudinal profiles in Figure 6, Figure 8 shows the trend of the calculated values of \(a_{z}\) that could be experienced on board at four speed values (i.e., 20 km/h, 30 km/h, 40 km/h, and 50 km/h). These values are even more than the administrative speed limit set for site 1b and 17, but they reflect the surveyed speed values. In regards to site 1b, Figure 8a,b represent the values of \(a_{z}\) and the elevation curve, respectively; Figure 8c,d refer to the values of \(a_{z}\) and the elevation curve of site 17. \begin{table}
\begin{tabular}{c c} \hline \hline
**Attribute** & **Number of RPCs (\% of RPCs)** \\ \hline Depressions before/after RPC & 5 (21\%) \\ Localized damages & 8 (34\%) \\ Horizontal markings on RPC ramps & 21 (88\%) \\ Horizontal markings before RPC & 4 (17\%) \\ Vertical signs & 24 (100\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Overview of visual survey results. Figure 4: Example of RPC. Figure 5: Example of surveyed distresses: (**a**) Depression on the access ramp; (**b**) depression after the exit ramp; (**c**) grooves on the pedestrian crossing surface; (**d**) grooves after the pedestrian crossing surface. Figure 6: Example of measured longitudinal RPC profile: (**a**) site 1b; (**b**) site 17. Figure 7: Empirical distribution of vehicle speed: (**a**) Frequency speed site 1b; (**b**) Cumulative frequency speed site 1b; (**c**) Frequency speed site 17; (**d**) Cumulative frequency speed site 17. Figure 8: Calculated \(a_{z}\) experienced on board compared to longitudinal profile of the RPC: (**a**) Sitelb \(a_{z}\) curve; (**b**) longitudinal profile of site 1b; (**c**) site 17 \(a_{z}\) curve; (**d**) longitudinal profile of site 17. Table 3 lists the obtained maximum and minimum values of \(a_{z}\) for car passengers passing through site 1b and site 17. Given the results of each survey/survey site, an aggregate analysis of the collected data was carried out in order to investigate the characteristics of RPCs.