Thepresent serviceability index (PSI) is a pavement performance measure. Introduced by theAmerican Association of State Highway and Transportation Officials (AASHTO), the PSI is one of the most widely used pavement performance indicators afterpavement condition index (PCI) andinternational roughness index (IRI).[1][2] This performance indicator ranges between 0 and 5, 0 representing a failed pavement and 5 an excellent one. Since the PSI entails slope variance, it is correlated withperformance indicators related to roughness such as IRI.[3]
The PSI was developed based on theAASHO Road Test'spresent serviceability rating (PSR).AASHO Road Test was a set of experiments carried out by theAASHTO from 1956 to 1961.[4] Unlike the PSR, which was a ride quality rating that required a panel of observers to ride in a car over the pavement of interest, the PSI does not require a panel of experts. Therefore, it was a more practical approach for large-scale pavement networks.
Present serviceability is a function of several variables. Forflexible pavement these variables include:[5]