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Roughness progression for a road in Texas, US. Blue dots show the times of maintenance. The international roughness index (IRI) is the roughness index most commonly obtained from measured longitudinal road profiles. It is calculated using a quarter-car vehicle math model, whose response is accumulated to yield a roughness index with units of ...
The pavement condition index (PCI) is a numerical index between 0 and 100, which is used to indicate the general condition of a pavement section.The PCI is widely used in transportation civil engineering [1] and asset management, and many municipalities use it to measure the performance of their road infrastructure and their levels of service. [2]
The present serviceability index (PSI) is a pavement performance measure.Introduced by the American Association of State Highway and Transportation Officials (AASHTO), the PSI is one of the most widely used pavement performance indicators after pavement condition index (PCI) and international roughness index (IRI).
Schematic deterioration of the condition of a road over time The increase in the IRI of a road in Texas. The blue dots on the curve represent maintenance actions. Pavement performance modeling or pavement deterioration modeling is the study of pavement deterioration throughout its life-cycle.
As an approximation, the roughness length is approximately one-tenth of the height of the surface roughness elements. For example, short grass of height 0.01 meters has a roughness length of approximately 0.001 meters. Surfaces are rougher if they have more protrusions. Forests have much larger roughness lengths than tundra, for example.
Advantages of contact profilometers include acceptance, surface independence, resolution, it is a direct technique with no modeling required. Most of the world's surface finish standards are written for contact profilometers. To follow the prescribed methodology, this type of profilometer is often required.
FWD data is most often used to calculate stiffness-related parameters of a pavement structure. The process of calculating the elastic moduli of individual layers in a multi-layer system (e.g. asphalt concrete on top of a base course on top of the subgrade) based on surface deflections is known as "backcalculation", as there is no closed-form solution.
Today TIR in its more inclusive expansion, "total indicator reading", concerns all kinds of features, from round to flat to contoured. One example of how the "total" emphasis can apply to flat surfaces as well as round ones is in the topic of surface roughness, where both peaks and valleys count toward an assessment of the magnitude of roughness.