Deterioration equivalence factors are an essential part of deterioration models used in pavement management systems. For accurate cost estimation, it is important to determine the correct axle load power. The data set from the AASHO Road Test was used to estimate a hazard rate function. The results showed that the axle load power for initiation of fatigue cracking was significantly higher than the power typically assumed. This result has implications for pavement deterioration charging schemes that are based on marginal cost pricing.