Fatigue cracking in asphalt concrete pavements is a major form of pavement distress in the United States. Currently, no effective tests and analysis protocols exist that can be easily and quickly performed by field engineers. To properly understand and model fatigue cracking over the range of conditions encountered in the field, without performing a large number of experiments, requires a mechanistic model. This model should describe the material responses to repeated loading, particularly the phenomena of crack initiation, coalescence, and finally propagation. Existing empirical techniques often smear these mechanisms into a predictive scheme by developing power law relationships between some input parameter (stress or strain) and the number of cycles to failure (Deacon et al. 1995). Another technique that is gaining support in the asphalt community is the continuum damage model.