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TRB's National Cooperative Highway Research Program (NCHRP) Web-Only Document 201: Calibration of AASHTO LRFD Concrete Bridge Design Specifications for Serviceability explores calibrating the service limit states related to concrete bridges in the American Association of State Highway and Transportation Officials' Load Resistance Factor Design Bridge Design Specifications (AASHTO LRFD). A limit state is defined as the boundary between acceptable and unacceptable performance of the structure or its component. According to the report, the limit states amenable to statistical calibration using the information currently available are cracking of reinforced concrete components, tensile stresses in concrete in prestressed concrete components, and fatigue of concrete and reinforcement The results of the work indicated that the main problem in calibrating the service limit states is the lack of clear consequences to exceeding the limit state and the ability to define more than one limit state function to address the same phenomenon. In the absence of reasons to increase or decrease the reliability inherent in the designs performed using the current specifications, the goal of the calibration was to help achieve uniform reliability with an average reliability similar to that inherent in current designs.