HFS Terminology

British Board of Agrément (BBA) – The UK’s major approval body for new construction products and installers.

Calcined Bauxite – extremely durable aggregate with a high PSV value. This type of has traditionally been the most commonly used aggregate for HFS.

High Friction Surfacing – a surface treatment possessing high friction properties. As defined in the BBA Guidelines Document, “a High-Friction Surface is defined as having a minimum SRV of 65 measured using the portable Skid-Resistance Tester”.

Highway Authorities Product Approval Scheme (HAPAS) – Organization in the UK developed to oversee the certification of innovative products, materials, and installers for highways use in the UK.

International Friction Index (IFI) – measurement of pavement macrotexture and wet pavement friction.

Mean Profile Depth (MPD) – the average of all mean segment depths of all segments of the profile.

Mean Texture Depth (MTD) – the mean depth of the pavement macrotexture profile determined by the volumetric technique of ASTM Test Method E 965.

Pavement Macrotexture – deviations of a pavement surface from true planar surface with wavelength characteristics from 0.5 mm to 50 mm.

Pavement Microtexture –  deviations of a pavement surface from true planar surface with wavelength characteristics less than 0.5 mm.

Pavement Surface Characteristic – a physical feature or property of a pavement surface (i.e. skid resistance, roughness, texture, type)

Portable Skid Resistance Tester – also known as the “Pendulum Tester”, measures the PSV and SRV of a surface.

Polished Stone Value (PSV) – value that gives a measure of the resistance to the polishing action of vehicle tires. The higher the PSV value, the more resistant the aggregate is to polishing.

Sideways Force Coefficient (SFC) – value of the skidding resistance obtained when using the SCRIM. SRV and SFC are not interchangeable.

Sideways Force Coefficient Routine Investigation Machine (SCRIM) – equipment used to determine the skidding resistance of a road surface, resulting in a SFC value.

Skid Number (SN) – value representing the skid of a surface obtained from using the locked-wheel trailer.

Skid Resistance – the ability of the traveled surface to prevent the loss of tire traction.

Skid Resistance Value (SRV) – a measure of skid from the actual road surface, usually determined by using the Portable Skid Resistance Tester. This value is dependent on the PSV of the aggregate and the macrotexture of the surface.

Wheel Path – the parts of the pavement surface where the majority of vehicle wheel passages are concentrated.