MPD/IRI Transverse Position


Road monitoring of the state road network in Sweden includes for the longitudinal measurement of international roughness index (IRI) and mean profile depth (MPD). In Sweden the paths of the longitudinal measurements correspond to the surface contact points between the wheels of a light passenger vehicle. This data can be used to estimate values for friction, rolling resistance, comfort and vehicle wear. Knowledge of the surface condition (IRI and MPD) at the surface contact points associated with a large goods vehicle would prove to be useful when estimating similar values for large goods vehicle on an entire or local road network. If these conditions are not measured, it is important to know how they differ from the measured path.

In Sweden, lateral position comparisons made between light and heavy vehicles show that left wheel track positions are similar. This applies to larger and wider roads (typical motorways and other wide main roads). Using this knowledge VTI’s measurement vehicle was equipped with two extra texture lasers which were mounted to the right of the ordinary texture laser in the right wheel track. Data was collected on a road network with mixed categories of road standard, from secondary roads to motorways.

In this talk, we will present a study of the differences of IRI and MPD corresponding to the position of light vehicles right wheel path with two other paths, 25 and 45 cm further out to the right (position of large goods vehicles). We also will discuss the possibility to predict the differences between the tracks. A statistical analysis procedure for calculating the mean difference and an error margin is suggested. The results showed that although it is very difficult to explain or predict local differences, average differences can be estimated.



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