# Sampietrini Stone Pavements: Distress Analysis Using Pavement Condition Index Method
## 3 Results and Discussions  
PCI values calculated for the sections examined in this paper, present a good variability going from 12 to 94, although just one section has PCI <40, corresponding to very poor pavement condition or worst. More details about the distresses presented in each inspected section are reported in Appendix B. As can be seen in Figure 7, a good correlation between PCI and IRI was found (\(R^{2}\) = 0.82). In particular, it can be noted that for good Sampietrini pavements (PCI > 86), IRI value varies between 6 and 8. These values, in case of rigid or flexible pavements, might be commonly associated to damaged pavement [11]. The peculiarity of IRI range values found for Sampietrini pavements is better underlined looking at Figure 8, where the relation between PCI and IRI for different types of pavement is depicted. \begin{table}
\begin{tabular}{c c} \hline \(a_{uv}\)**Values (m/s\({}^{2}\))** & **Comfort Level** \\ \hline \(<\)0.315 & Not uncomfortable \\
0.315–0.63 & A little uncomfortable \\
0.5–1 & Farity uncomfortable \\
0.8–1.6 & Uncomfortable \\
1.25–2.5 & Very uncomfortable \\ \(>\)2 & Extremely uncomfortable \\ \hline \end{tabular}
\end{table} 
Table 4: Comfort levels related to \(a_{uv2}\) threshold values proposed by ISO 2631 for public transport. Figure 8: Correlation between PCI and IRI for a different type of pavements. Figure 7: Correlation between Pavement Condition Index (PCI) and International Roughness Index (IRI) for Sampietrini pavements. In particular, it can be seen that, according to the relations found by [PERSON] et al. [12], regardless of the type of pavements, IRI values are always lower than 10 m/km, even for PCI close to 0. Considering the relation found by [PERSON] et al. [29] for asphalt pavements, instead, for PCI values lower than 40 (corresponding to pavements condition from very poor to failed, see Table 2) very high values of IRI are found. In any case, it is clear that different IRI values must be associated to new or reconstructed Sampietrini pavements, compared to the most common types of pavement (flexible and rigid). Starting from this result, it was decided to evaluate the ride quality perceived by road users traveling along Sampietrini pavements at different speeds. As already stated, taking into account that this type of pavement is present just in urban areas, velocity range between 10 and 50 km/h was considered. As can be seen in Figure 9, very weak correlations (\(R^{2}\) = 0.44-0.70) were found between IRI and \(a_{uzz}\) values at different speeds. Similar results, in terms of correlation coefficient \(R^{2}\), were obtained comparing PCI and \(a_{uzz}\) approaches (Figure 10). In fact, as depicted in Figure 11, \(R^{2}\) values at different speeds for IRI-\(a_{uzz}\) and PCI-\(a_{uzz}\) correlations are very close to each other. Figure 10: Correlation between PCI and \(a_{uzz}\) at different speeds. Figure 9: Correlation between IRI and \(a_{uzz}\) at different speeds. Considering for example two sections having PCI >85 (corresponding to a pavement in good condition), it is possible to evaluate the comfort level induced on road users traveling at different velocities on new or reconstructed Sampietrini pavements. As can be seen in Figure 12, also moving at 50 km/h (maximum legal speed allowed on Italian urban roads) the worst comfort level perceived by drivers is equal to \"fairly uncomfortable\". In the same figure, two sections characterized by PCI values between 41 and 55 (corresponding to poor pavement condition) are also reported. In this case, at the maximum allowable speed (i.e., 50 km/h), the comfort level was found to be very uncomfortable. Furthermore, levels equal to fairly uncomfortable/uncomfortable are already reached at 30 km/h. The aforementioned results show the chance of using Sampietrini pavements on the urban road network, allowing a little level of discomfort on users.