As a support for controlling the implementation of the unevenness indices calculation, three longitudinal profiles are available. The profiles represent low, medium and high unevenness. A true value for each is also available. The longitudinal profiles are 1000 meter long divided into 0.125 meter steps and have the vertical unit millimetre. They can be downloaded from www.erpug.org under the directory reference profiles.
The true IRI value is calculated with Δx=0.125 m and presented as an average per 20 meter.