Texture (roads)

Road surface textures are deviations from a planar and smooth surface, affecting the vehicle/tyre interaction. Pavement texture is divided into: microtexture with wavelengths from 0 mm to 0.5 millimetres (0.020 in), macrotexture with wavelengths from 0.5 millimetres (0.020 in) to 50 millimetres (2.0 in) and megatexture with wavelengths from 50 millimetres (2.0 in) to 500 millimetres (20 in).

Microtexture (MiTx) is the collaborative term for a material's crystallographic parameters and other aspects of micro-structure: such as morphology, including size and shape distributions; chemical composition; and crystal orientation and relationships

While vehicle suspension deflection and dynamic tire loads are affected by longer wavelength (roughness), road texture affects the interaction between the road surface and the tire footprint. Microtexture has wavelengths shorter than 0.5 mm. It relates to the surface of the binder, of the aggregate, and of contaminants such as rubber deposits from tires.

The mix of the road material contributes to dry road surface friction. Typically, road agencies do not monitor mix directly, but indirectly by brake friction tests. However, friction also depends on other surface properties, such as macro-texture.

Macrotexture (MaTx) is partly a desired property and partly an undesired property. Short MaTx waves, about 5 mm, act as acoustical pores and reduce tyre/road noise. On the other hand, long wave MaTx increase noise. MaTx provide wet road friction, especially at high speeds. Excessive MaTx increases rolling resistance and thus fuel consumption and CO₂ emission contributing to global warming. Proper roads have MaTx of about 1 mm Mean Profile Depth.

Macrotexture is a family of wave-shaped road surface characteristics. While vehicle suspension deflection and dynamic tyre loads are affected by longer waves (roughness), road texture affects the interaction between the road surface and the tyre footprint. Macrotexture has wavelengths from 0.5 mm up to 50 mm.

Road agencies monitor macrotexture using measurements taken with highway speed laser or inertial profilometers.

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