TRB's National Cooperative Highway Research Program (NCHRP) Web-Only Document 108: Guide for Pavement Friction examines the management of pavement friction on existing highways and explores the design of new highway surfaces with adequate pavement friction. The report also highlights the importance of pavement friction in highway safety; factors affecting pavement friction; and the equipment, procedures, and indices that may be used to quantify and report available friction.  Background on the project and information on research related to the development of Web-Only Document 108 was published as NCHRP Research Results Digest 321: Guide for Pavement Friction: Background and Research.