I support the good answer stated by dear Rawand. To complete the mentioned explanation, it may be noted that the primary factor which is used in the existing literature to determine the PSI may be considered to be longitudinal roughness. Thus, some researchers have not used the other factors, e.g. cracking, patching, etc., in their correlations. Therefore, PSI may be determined solely by the use of pavement roughness, especially for the rural pavements, with a high degree of accuracy.