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Moving to International Roughness Index Measured by Inertial Profilers in an End Result Specification for New Asphalt Construction in Ontario


The smoothness of new pavements constructed for the Ontario Ministry of Transportation (MTO) is accepted on the basis of Profile Index (PI), as measured by California Profilographs. Since these 7.6 m long devices are difficult to handle, operated at walking speeds (3-5 km/hr) and can only measure one wheelpath at a time, the MTO and the hot mix industry have been looking for an alternative device that would be easier and safer to operate. This paper summarizes the results of two field studies which were conducted using laser inertial profilers consisting of “lightweight” profilers, operated at speeds of 15 to 20 km/hr and “high speed” profilers which can be operated at highway speeds. Both kinds of devices can also measure both wheelpaths simultaneously in units of both Profile Index (PI) and International Roughness Index (IRI). Since inertial profilers take measurements much faster than California Profilographs, they cause less disruption to traffic and are inherently much safer to operate. The objectives of this study were to determine if: I. Inertial profilers can replace California Profilographs, II. IRI can be used as an acceptance attribute for new construction to replace PI, and III. IRI measurements produced by inertial profilers could be integrated into a network data base for the long term monitoring of Ontario’s pavements. During the fall of 2003, three lightweight profilers, three California Profilographs and a high speed Automated Road Analyzer (ARAN) measured 15 pavement sections in Eastern Ontario. In addition, a 2007 study compared a single profilograph with three high speed profilers on two asphalt sections in Central Ontario. The correlation between PI (by the California Profilographs) and IRI (by inertial profilers) were excellent and the results can be used to develop IRI-based acceptance criteria “equivalent” to the PI-based ones. Based on the results of these studies, inertial profilers can be used to replace California Profilographs for the acceptance of new pavement construction and IRI measurements can also be integrated into the long term monitoring of Ontario’s new pavements. As Ontario moves toward implementing inertial profilers for the smoothness acceptance of new construction, much faster measurements, less disruption to traffic and improved operator safety are expected to be realized.

Conference Paper Details

Session title:
John A. Blair
Kai K. Tam