There are two types of precast headwalls, attached and detached. Attached headwalls are cast onto the end unit at the plant and are shipped to the jobsite as one piece. Detached headwalls are match cast against their end units, shipped separately to the site and are attached with stainless steel hardware. Shipping height and/or weight issues dictate which one is used. Both types may be designed for AASHTO bridge rail loading and can accommodate concrete barrier or steel railings. Headwall thickness ranges from 8 to 15 with 12 being the standard and headwall heights at the crown of the arch can vary from 6 inches to over 6 feet depending on the loading. Headwalls are designed to accommodate roadway grade, can be sloped and are easily enhanced with architectural treatments.