as when obtaining IRI values, while macrotexture is the measurement of the individual variations of the road within a small interval of a few centimeters. For example, a road which has gravel spread on top followed by an asphalt seal coat will have a high macrotexture, and a road built with concrete slabs will have low macrotexture. For this reason, concrete is often grooved or roughed up immediately after it is laid on the road bed to increase the friction between the tire and road. Equipment to measure macrotexture currently consists of a distance measuring laser with an extremely small spot size (< 1 mm) and data acquisition systems capable of recording elevations spaced at a mm or less apart. The sample rate is generally over 32 kHz. Macrotexture data can be used to calculate the speed-depending part of the friction number between typical car tires and the road surface. The macrotexture also give information on the difference between dry and wet road friction. However, macrotexture cannot be used to calculate a relevant friction number, since also microtexture affects the friction. Lateral friction and cross slope are the key reaction forces acting to keep a cornering vehicle in steady lateral position, while exposed to exciting forces from speed and curvature. Since friction is strongly dependent on macrotexture and texture, cross slope as well as curvature can be measured with a road profiler, so road profilers are very useful to identify improperly banked curves that may pose a risk to motor vehicles. See also Road Roughness Rut (roads) Superelevation Profilometer Ride quality References Road infrastructure Pavement engineering