**5. Findings**

The influence of all of the distress types that are present in the study area, on the IRI measurement was analyzed in order to study the riding quality-related types of distress. From the main street sections, six distress groups exist in the Riyadh network samples. While the secondary streets involve five distresses groups. Tables 6 and 7 conclude the final analysis of the relationship between the roughness evaluation index (IRI) and the pavement

distress density for both main and secondary streets, sequentially. The correlation between the value of IRI and distress types has been investigated by two important statistical tests:


**Table 6.** Summary of correlation factors and regression models in main street sections.


**Table 7.** Summary of correlation factors and regression models in secondary street sections.


Tables 6 and 7 show that *p*-values for cracking, depression, patching, and raveling in both main and secondary streets are near zero, indicating a significant relationship between these distress types and IRI. As a result, the findings of the research in both the main and secondary street categories suggests that there is a significant relationship between IRI and cracking, patching, depression, and raveling with a 95% confidence level. Statistical testing on the overall model between IRI and distress types confirmed these findings. The *p*-values for each regression coefficient were obtained in the regression coefficients test. In both the major and subsidiary streets, the regression coefficients for cracking, depression, patching,

and raveling are close to zero (less than 0.05), indicating a substantially linear relationship between IRI and each regression coefficient. IRI is related to different types of distress in different ways. Patching and depression had the highest correlation to IRI, according to the values of the correlation factors. While raveling has a lower relationship with IRI, cracking has the lowest. It was also found that the correlation factors for all the distresses versus IRI did not reach 50%, meaning that the relationship describes less than half of these relationships. The relationship is not strong enough to consider pavement conditions as an indicator of IRI. As a result, the correlation and regression coefficients testing showed that cracking, patching, depression, and raveling are ride quality types of distress with a 95% confidence level. However, it is unrealistic to claim that IRI can completely describe pavement distress conditions.

It's also shown in Tables 6 and 7, that potholes and rutting, point toward a relationship that is not significant with IRI values in both the main and secondary streets. The *p* values (which are larger than 0.05 level of significance) of both potholes and rutting demonstrates that these distress types have no strong evidence of a significant relationship with IRI. These results were proven through the statistical tests on the overall model between IRI and distress types. The *p*-values for each regression coefficient were obtained in the regression coefficients test. Potholes and rutting have regression coefficients larger than 0.05, meaning that there is no significant linear relationship between IRI and each distress type. As a result, the correlation and regression coefficient tests show that potholes and rutting are non-ride quality distress types and that IRI could not describe potholes and rutting distress conditions with 95 percent confidence.
