Road surface textures are deviations from a planar and smooth surface, affecting the vehicle/tyre interaction. Pavement texture is divided into:

microtexture 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 , macrotexture with wavelengths from to and megate ...

with wavelengths from 0 mm to ,

macrotexture 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 , macrotexture with wavelengths from to and megatext ...

with wavelengths from to and

megatexture id Tech 4, popularly known as the ''Doom 3'' engine, is a game engine developed by id Software and first used in the video game ''Doom 3''. The engine was designed by John Carmack, who also created previous game engines, such as those for ''Doo ...

with wavelengths from to .

Microtexture

Microtexture (MiTx) is the collaborative term for a material's

crystallographic Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics ( condensed matter physics). The w ...

parameters and other aspects of micro-structure: such as

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

, including size and shape distributions;

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...

composition; and

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

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 Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

tests. However, friction also depends on other surface properties, such as macro-texture.

Macrotexture

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 A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

and CO₂ emission contributing to

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. 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.

Megatexture

Megatexture (MeTx) is a result of pavement wear and distress, causing noise and vibration. Megatexture has wavelengths from 50 mm up to 500 mm. Some examples of road damages with much MeTx are potholes, washboards (common on dirt roads) and uneven frost heaves. MeTx below 0.2 mm Root-Mean-Square is considered normal on proper roads.

Measurement

MaTx and MeTx are measured with laser/inertial

profilograph 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 , macrotexture with wavelengths from to and megatex ...

s. Since MiTx has so short waves, it is preferably measured by dry friction brake tests rather than by profiling. Profilographs that record texture in both left and right wheel paths can be used to identify road sections with hazardous

split friction Split friction (or μ (mu) - split) is a road condition that occurs when the friction significantly differs between the left and the right wheelpath. The road may then not be perceived as hazardous when accelerating, cruising or even braking soft ...

Profilograph

The profilograph is a device used to measure pavement surface roughness. In the early 20th century, profilographs were low speed rolling devices (for example

rolling straight-edge The rolling straight-edge (also rolling straightedge or planograph) is an instrument used to measure the surface regularity of roads and similar structures such as airport runways. It consists of a straightedge of a fixed distance mounted on whe ...

s). Today many profilographs are advanced high speed systems with a laser based height sensor in combination with an inertial system that creates a large scale reference plane. It is used by construction crews or certified consultants to measure the roughness of in-service road networks, as well as before and after milling off ridges and paving overlays. Modern profilographs are fully computerized instruments. The data collected by a profilograph is used to calculate the International Roughness Index (IRI), which is expressed in units of inches/mile or mm/m. IRI values range from 0 (equivalent to driving on a plate of glass) upwards to several hundred in/mile (a very rough road). The IRI value is used for road management to monitor road safety and quality issues. Many road profilographs are also measuring the pavements

cross slope Cross slope, cross fall or camber is a geometric feature of pavement surfaces: the transverse slope with respect to the horizon. It is a very important safety factor. Cross slope is provided to provide a drainage gradient so that water will run ...

, curvature, longitudinal

gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gr ...

and rutting. Some profilographs take digital

photo A photograph (also known as a photo, image, or picture) is an image created by light falling on a photosensitive surface, usually photographic film or an electronic image sensor, such as a CCD or a CMOS chip. Most photographs are now crea ...

s or

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syst ...

s while profiling the road. Most profilographs also record the position, using

GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

technology. Yet another common measurement option is cracks. Some profilograph systems include a

ground penetrating radar Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. It is a non-intrusive method of surveying the sub-surface to investigate underground utilities such as concrete, asphalt, metals, pipes, cables ...

, used to record

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

layer thickness. Another type of profilograph system is for measuring the surface

texture Texture may refer to: Science and technology * Surface texture, the texture means smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface characteristics with waves shorter than road roughness * Texture ...

of a road and how it relates to the coefficient of

and thus to

skid resistance Road slipperiness is a condition of low skid resistance due to insufficient road friction. It is a result of snow, ice, water, loose material and the texture of the road surface on the traction produced by the wheels of a vehicle. Road slipperi ...

. Pavement texture is divided into three categories; megatexture, macrotexture, and microtexture. Microtexture cannot currently be measured directly, except in a laboratory. Megatexture is measured using a similar profiling method 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 1 mm or less. The sample rate is generally over 32 kHz. Macrotexture data can be used to calculate the speed-dependent part of friction between typical car tires and the road surface in both dry and wet conditions. Microtexture affects friction as well. Lateral friction and cross slope are the key reaction forces acting to keep a cornering vehicle in steady lateral position, while it is subject to exiting forces arising from speed and curvature. Cross slope and curvature can be measured with a road profilograph, and in combination with friction-related measurements can be used to identify improperly banked curves, which can increase the risk of motor vehicle accidents.

Road profilometery{{anchor, Profilometery

Road pavement profilometers (aka

s, as used in the famous 1958-1960

AASHO Road Test The AASHO Road Test was a series of experiments carried out by the American Association of State Highway and Transportation Officials (AASHTO), to determine how traffic contributed to the deterioration of highway pavements. Methodology Of ...

) use a distance measuring laser (suspended approximately 30 cm from the pavement) in combination with an odometer and an

inertial In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration. ...

unit (normally an

accelerometer An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is acc ...

to detect vehicle movement in the vertical plane) that establishes a moving reference plane to which the laser distances are integrated. The inertial compensation makes the profile data more or less independent of what speed the profilometer vehicle had during the measurements, with the assumption that the vehicle does not make large speed variations and the speed is kept above 25 km/h or 15 mph. The profilometer system collects data at normal highway speeds, sampling the surface elevations at intervals of 2–15 cm (1–6 in), and requires a high speed data acquisition system capable of obtaining measurements in the kilohertz range. The data collected by a profilometer is used to calculate the International Roughness Index (IRI) which is expressed in units of inches/mile or mm/m. IRI values range from 0 (equivalent to driving on a plate of glass) upwards to several hundred in/mi (a very rough road). The IRI value is used for road management to monitor road safety and quality issues. Many road profilers also measure the pavement's

, curvature, longitudinal

and rutting. Some profilers take digital

s or

s while profiling the road. Most profilers also record the position, using

technology. Another quite common measurement option is cracks. Some profilometer systems include a

, used to record

layer thickness. Another type of profilometer is for measuring the surface texture of a road and how it relates to the coefficient of

and thus to

. Pavement texture is divided into three categories: megatexture, macrotexture, and microtexture. Microtexture cannot currently be measured directly, except in a laboratory. Megatexture is measured using a similar profiling method 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.

References

Road infrastructure Pavement engineering

Microtexture

Macrotexture

Megatexture

Measurement

Profilograph

Road profilometery{{anchor, Profilometery

See also

References