4.1 This guide provides information to assist engineers with the design requirements and construction guidelines for paving an Open-Graded Friction Course (OGFC) surface layer. An OGFC is primarily used to improve the skid resistance and wear resistance of a bituminous pavement by providing an escape route for surface water beneath a moving wheel load. The mixture is typically produced with a low amount of fine aggregate particles and high air void content to provide a passageway of interconnected voids for moisture to drain away from the travelway. The film thickness of the asphalt and overall asphalt content is important for better stripping resistance and durability and aging properties.

1.1 This guide covers the construction of bituminous open-graded friction course plant mixtures. End-use specifications should be adopted to conform to job and user requirements. Where applicable, Specification D3666 should be applied as a minimum for agencies testing and inspecting road and paving materials.

1.2 Bituminous open-graded friction courses are placed as the final wearing course for highways and airfields.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.