Underseals may be applied to the surface of an existing pavement prior to the placement of a new surface lift of HMA for two primary reasons. The first is to seal the old HMA layer, which has small to moderate amounts of cracking or is otherwise permeable because of poor compaction. The other reason is to improve the adhesion or bond of the new surface lift of HMA to the existing structure. Item 316 is the governing specification. Cautions cited above regarding the stripping susceptibility of the existing HMA layers apply with application of underseals as well.