Critical Review and Potential Improvement of the New International Airport Pavement Strength Rating System

Most airports rate and publish the strength of their runway pavement using the international system known as Aircraft Classification Number–Pavement Classification Number (ACN–PCN). The ACN–PCN system has been in place since 1981 and includes many simplifications that were necessary at the time of its development, primarily due to the general absence of computer power to support more sophisticated analysis. However, airport pavement thickness determination has evolved since that time and now includes much more sophisticated analysis methods. To bring the strength rating system into line with contemporary pavement thickness determination methods, a new system has been developed, known as Aircraft Classification Rating–Pavement Classification Rating (ACR–PCR). This critical review found that ACR–PCR provides many improvements over ACN–PCN, including minimizing anomalies between pavement thickness design and subsequent pavement strength rating, the use of more representative aircraft traffic loadings and pavement structures, and the alignment of rigid and flexible subgrade support categories. However, ACR–PCR could be improved with regard to the representative subgrade characteristic values, the retention of an overly simple tire pressure category limit approach for surface protection, the provisions for single-wheeled light aircraft pavements, and the absence of a rational approach to strength rating that is substantially better than a usage-based approach but does not necessarily follow the formalized technical rating protocol. Despite these limitations, the current ACN–PCN system has been in place for over 40 years without significant change, so it is expected that ACR–PCR will be in place for many years as well. Consequently, airports should prepare for its imminent introduction, regardless of the associated limitations.