In the ASTM E 867-06 test standard,[4] the concept of Roughness is defined as: “deviation of a given surface with respect to a theoretical flat surface, with dimensions that affect vehicle dynamics, handling quality, dynamic loads and drainage, for example, longitudinal profile, transverse profile.”.

The standard that refers to the nature and measurement of the IRI is NLT-330/98.[5]​.

To calculate the IRI value, broadly speaking, we proceed in two steps:

Initially, the elevations of the terrain are measured, which allows us to create a longitudinal profile of the road. The data of this profile is subjected to a first filter, which, through mathematical adjustments (moving average), generates a new corrected profile.

A second filter is applied to this corrected profile, consisting of the application of the quarter car model developed previously.

Finally, the IRI is defined as the sum of measured distances, modulo above the horizontal, for the distance considered. In module it means that they compute both the increases and decreases in height on the horizontal → in the end both displacements represent a variation in the vertical of the suspended mass.

In short, we have come to the conclusion that the IRI is nothing more than the value of the accumulated vertical movement of the driver's seat of the vehicle over a given distance. It is, therefore, instinctive to think that the greater the irregularity in the road surface, the vertical displacements on the theoretical horizontal, and, consequently, the value of the IRI, will be greater → the value of the IRI will be better the closer we get to the theoretical flat surface, taking into account that this concept is utopian, since a minimum of roughness is needed to guarantee wheel-pavement adhesion.

Today, there are many devices capable of measuring IRI. After all, the starting data to obtain the IRI are nothing more than a “longitudinal profile” of the road surface.

Along these lines, it would be possible to determine the IRI from equipment as simple as a sight and a level → The level establishes the horizontal, and with the sight we obtain the points of the longitudinal profile. The drawback is that for long distances, the work can become long and tedious.

The Dipstick consists of an inclinometer held between two supports separated by 300 mm or 250 mm (depending on the units of analysis, the supports can be separated by 12 inches), which records the elevation of one support relative to the elevation of the other.

profilers have a sensitive wheel, mounted in the center of the frame that can keep vertical movement free. The deviation about the reference plane, established by the profilograph frame, is recorded (automatically in some models) on paper according to the movement of the sensitive wheel. They can be found in a wide variety of shapes, configurations and brands.

The drawback posed by all the equipment shown so far (some more than others) is the poor performance in terms of distance coverage. Given the large number of kilometers available in the different road networks, and the need to undertake them in a reasonably short time, high performance equipment emerged to measure the IRI:.

Response Type or RTRRMS equipment works at the normal speed of the road they are measuring. The RTRRMS equipment technology is based on measuring the vertical movements of the rear axle of the car with respect to the vehicle frame. The equipment therefore measures the reaction or rebound of the vehicle to the regularity of the road, so it is not really a true measure of the smoothness of the surface.

Inertial profilometers are high-performance equipment, which based on devices such as gyroscopes and accelerometers, produce automatic and high-quality measurements of the road profile. The most widespread are laser profilometers, which have laser devices to measure the profile, and which, combined with this system of gyroscopes and accelerometers, allow extremely high precision measurements to be obtained at standard traffic speeds (80-100 km/h).

Today they are the most used to determine the value of the IRI, as well as other parameters, such as macrotexture.

In the ASTM E 867-06 test standard,[4] the concept of Roughness is defined as: “deviation of a given surface with respect to a theoretical flat surface, with dimensions that affect vehicle dynamics, handling quality, dynamic loads and drainage, for example, longitudinal profile, transverse profile.”.

The standard that refers to the nature and measurement of the IRI is NLT-330/98.[5]​.

To calculate the IRI value, broadly speaking, we proceed in two steps:

Initially, the elevations of the terrain are measured, which allows us to create a longitudinal profile of the road. The data of this profile is subjected to a first filter, which, through mathematical adjustments (moving average), generates a new corrected profile.

A second filter is applied to this corrected profile, consisting of the application of the quarter car model developed previously.

Finally, the IRI is defined as the sum of measured distances, modulo above the horizontal, for the distance considered. In module it means that they compute both the increases and decreases in height on the horizontal → in the end both displacements represent a variation in the vertical of the suspended mass.

In short, we have come to the conclusion that the IRI is nothing more than the value of the accumulated vertical movement of the driver's seat of the vehicle over a given distance. It is, therefore, instinctive to think that the greater the irregularity in the road surface, the vertical displacements on the theoretical horizontal, and, consequently, the value of the IRI, will be greater → the value of the IRI will be better the closer we get to the theoretical flat surface, taking into account that this concept is utopian, since a minimum of roughness is needed to guarantee wheel-pavement adhesion.

Today, there are many devices capable of measuring IRI. After all, the starting data to obtain the IRI are nothing more than a “longitudinal profile” of the road surface.

Along these lines, it would be possible to determine the IRI from equipment as simple as a sight and a level → The level establishes the horizontal, and with the sight we obtain the points of the longitudinal profile. The drawback is that for long distances, the work can become long and tedious.

The Dipstick consists of an inclinometer held between two supports separated by 300 mm or 250 mm (depending on the units of analysis, the supports can be separated by 12 inches), which records the elevation of one support relative to the elevation of the other.

profilers have a sensitive wheel, mounted in the center of the frame that can keep vertical movement free. The deviation about the reference plane, established by the profilograph frame, is recorded (automatically in some models) on paper according to the movement of the sensitive wheel. They can be found in a wide variety of shapes, configurations and brands.

The drawback posed by all the equipment shown so far (some more than others) is the poor performance in terms of distance coverage. Given the large number of kilometers available in the different road networks, and the need to undertake them in a reasonably short time, high performance equipment emerged to measure the IRI:.

Response Type or RTRRMS equipment works at the normal speed of the road they are measuring. The RTRRMS equipment technology is based on measuring the vertical movements of the rear axle of the car with respect to the vehicle frame. The equipment therefore measures the reaction or rebound of the vehicle to the regularity of the road, so it is not really a true measure of the smoothness of the surface.

Inertial profilometers are high-performance equipment, which based on devices such as gyroscopes and accelerometers, produce automatic and high-quality measurements of the road profile. The most widespread are laser profilometers, which have laser devices to measure the profile, and which, combined with this system of gyroscopes and accelerometers, allow extremely high precision measurements to be obtained at standard traffic speeds (80-100 km/h).

Today they are the most used to determine the value of the IRI, as well as other parameters, such as macrotexture.