PURPOSES : The objective of this study is to develop a pavement rehabilitation decision tree considering current pavement condition by evaluating severity and distress types such as roughness, cracking and rutting. METHODS: To improve the proposed overall rehabilitation decision tree, current decision tree from Korea and decision trees from other countries were summarized and investigated. The problem when applying the current rehabilitation method obtained from the decision tree applied in Seoul was further analyzed. It was found that the current decision trees do not consider different distress characteristics such as crack type, road types and functions. Because of this, different distress values for IRI, crack rate and plastic deformation was added to the proposed decision tree to properly recommend appropriate pavement rehabilitation. Utilizing the 2017 Seoul pavement management system data and considering all factors as discussed, the proposed overall decision tree was revised and improved. RESULTS: In this study, the type of crack was included to the decision tree. Meanwhile current design thickness and special asphalt mixture were studied and improved to be applied on different pavement condition. In addition, the improved decision tree was incorporated with the Seoul asphalt overlay design program. In the case of Seoul's rehabilitation budget, rehabilitation budget can be optimized if a 25mm milling and overlay thickness is used. CONCLUSIONS: A practical and theoretical evaluation tool in pavement rehabilitation design was presented and proposed for Seoul City.

PURPOSES : So far, aged cement concrete pavement on express highways has been rehabilitated mainly with asphalt concrete inlay. However, potholes were the major problem, and they shortened the life of the inlay mainly owing to the poor drainage of water once it infiltrated the interface of the concrete and asphalt. The purpose of this study is to compare the performance and economic efficiency of asphalt overlay and inlayMETHODS: Overlay and inlay were compared through accelerated pavement testing, and a life-cycle cost analysis was conducted in this study using the CA4PRS program.RESULTS and CONCLUSIONS : It was found from accelerated pavement testing that the overlay exhibited reflective crack resistance that was more than twice as effective as that of inlay. The total cost (construction cost + user cost) within the analysis period (20 years) of the overlay was 37% lower than that of the inlay.

PURPOSES : The PMS(Pavement Management System) has been utilized in order to efficiently allocate the limited budget for the maintenance of national highway system. In the PMS of national highway, surface pavement condition is evaluated by using the VI (Visual Index). However, the VI is determined only by considering the cracking rate (%) and rut depth (mm), which is not reflecting the IRI (International Roughness Index) that is known as an important factor of pavement performance. In this study, the NHPCI (National Highway Pavement Condition Index) which includes the cracking rate (%), rut depth (mm), and IRI (m/km) is suggested for determining the rehabilitation methods group. METHODS : First, the rehabilitation methods performed between 2008 and 2010 on the national highway is classified and then, NHPCI is determined for each rehabilitation method. Next, the NHPCI for each rehabilitation method is grouped through the interval estimation of the population mean and T-test analysis. RESULTS : According to NHPCI range, the rehabilitation methods are divided into four categories: Not Required, Preventive Maintenance, Overlay Treatment (with or without cutting), and Full-scale Treatment (i.e., reconstruction). CONCLUSIONS : Based on this study, it is recommended that the appropriate NHPCI range should be determined through the combination of the rehabilitation categories and Decision Procedure of Pavement Distress Condition Visual Index.