Flexible pavements, surfaced with hot mix asphalt (HMA), are the prevalent pavement structures in
Canada and elsewhere. HMA, also called asphalt concrete (AC), overlays are the common treatments to
extend their lifecycle. Commonly used AC overlay design methods, e.g., AASHTO 1993, have been
providing reasonable trends of design outcomes. However, there are still some concerns related to the
outcomes from the AASHTOWare Pavement ME Design (PMED) software. This study evaluates the
suitability of the latest version (v3.0) of the PMED software for AC overlay design.
Several overlay design trials for three existing pavements with varying strength, surface condition, layer
materials, subgrade type, existing AC mill depth, overlay thickness and traffic loads were completed for
nine climatic areas. Analysis showed that AC overlays on milled surfaces result in no reduction in
roughness and an increase in total rutting as compared to straight overlays. An increased overlay thickness results in inconsistent variation of the predicted total rutting. Increased traffic loads result in increased roughness, total rutting and AC layer rutting with some inconsistencies and unexpected variations among climatic areas. The total rutting values in overlaid pavements are governed by rutting in subgrade and granular material layers despite that there was no rutting in those materials of the existing pavements. No design input affects the predicted bottom‐up fatigue cracking (BUFC) and top‐down fatigue cracking (TDFC), except traffic load. Higher fatigue cracking in existing pavements correspond to higher reflective cracking with inconsistencies among climatic areas. Increased mill depths provide no or unexpected effect on the predicted reflective cracking. There is no or negligible variation of transverse cracking among input variables. Transverse reflective cracking is unaffected by milling or overlay thickness with some exceptions and inconsistencies.