Abstract:This is the second of two reports that present fatigue cracking performance models for asphalt concrete overlays placed on existing asphalt concrete pavement. The models were developed from the pavement management system (PMS) database of the Washington State Department of Transportation (WSDOT). The database included existing pavement structure, overlay thickness and type, truck traffic, and observed percent of the wheelpath cracked from annual condition surveys. Climate data was developed by the UCPRC to augment the WSDOT data. This report presents a model for crack propagation, starting from crack initiation, which was defined as 5 percent of the wheelpath with longitudinal cracking. The combined initiation and propagation models were included in a spreadsheet calculator which was used to perform an analysis of the sensitivity of crack initiation and propagation to the input variables. The models are extremely useful for predicting pavement performance. For use in California they will need recalibration of the coefficients to reflect differences in WSDOT and California practice, primarily the use of thicker overlays in California, placement of overlays at much more advanced states of cracking in the existing pavement, and possible differences in routine maintenance activities.