Illustration of the IRI scale for different pavementseIRI (estimated International Roughness Index, expressed in m/km): an international measure of road roughness as it acts on a vehicle. Roughness is expressed as the vertical movement of the suspension (in metres) per kilometre travelled. The higher the IRI, the less comfortable the road and the lower the speed at which it can still be driven comfortably. This is an important measure of the current quality of the pavement, including the foundation. On the detail page of a road, the 85th percentile of the eIRI is shown next to the average (eIRI (85th pct)).
Speed-related IRI thresholds according to Yu et al. (National Taipei University of Technology)Driving Quality: an interpreted version of the eIRI in which the driven speed is linked to the IRI to determine whether the road still fulfils its function. This uses the table from the research of the National Taipei University of Technology. The speed used is the 85th percentile of all measurements on the road section (85 % of the vehicles drive slower than this speed). The classes are Very Good, Good, Fair, Mediocre and Poor.
Reference speed: the 85th percentile of the measured driving speeds on the road section, in km/h. This speed is used to determine the Driving Quality and is in itself a useful indication of how the road is used.
Surface Type: the type of pavement – asphalt, concrete, brick, cobblestone or other. The surface type is estimated automatically from the measurements. As long as this estimate still changes between successive measurement rounds, the portal shows the label ESTIMATE. You can record the surface type yourself with an annotation of type Surface. The applicable annotation takes precedence over the estimate and is marked on the detail page with ANNOTATED. A current annotation may differ from the surface type in a monthly report; see Current surface type and monthly report.
Authority (road authority): the body that manages the road (for example the city or municipality, the Flemish Agency for Roads and Traffic (AWV) or a private owner). This lets you limit the results to the roads you are responsible for.
