For Flexible Pavements, iteration is done two different ways. If only the total AC thickness is needed, then the user inputs a minimum AC thickness and a set thickness for each base layer. Once these are entered by the user, then PAVEXpress determines the total asphalt thickness to the nearest ½” based on the traffic loadings and subgrade strength. If the user wants to select the multiple lift approach for the asphalt layers, then the asphalt surface and intermediate/binder thickness is entered and PAVEXpress iterates on the bases asphalt layer thickness to the nearest ½” based on the traffic loadings and subgrade strength. For Rigid Pavements, the only approach is iterating on the final concrete slab thickness to the nearest ½” based on traffic loadings and subgrade strength.