Transfer Function

Transfer functions convert the predicted damages into the extent of observable pavement distresses. Typically each distress has its own set of corresponding damages. For example, surface cracking is typically correlated with bottom-up fatigue damage. Some M-E method also adds contribution to surface cracking from top-down fatigue cracking. Each distress has its own transfer function.

Transfer functions are typically developed through the field calibration process, in which correlation is established between predicted damages and the observed distress.

Transfer functions are the key components that bridge the relative simplicity of computer modeling with the complications and randomness of field performances. It is important to keep in mind that pavement performances are never really random. They seem random because many of the factors affecting them can be random. For example, material deflects can happen randomly both within a project, and across different projects. The transfer functions should be formulated properly to account for this randomness.

This part of the M-E method is empirical.