The most common types of asphalt surfaces used to upgrade frictional characteristics of pavements are seal coats, open-graded mixes, and dense-graded mixes. This report of the Transportation Research Board provides information on current engineering practices, legal and regulatory considerations, and criteria for selection of appropriate types of asphalt friction courses.   The report for this topic can be purchased at https://www.trb.org/news/blurb_detail.asp?id=3453