During the fall of 1989, the Illinois Department of Transportation completed the construction of a profile-measuring van that was based on the South Dakota road profiler. One feature of the van is the ability to collect rut depths at highway speed at 2-ft intervals. The ability to collect more rut data and to do it more quickly and safely were of great interest to the department. However, no information was available that described how the data obtained with the road profiler would compare with manual rut measurements or rut measurements obtained with other automated systems. In an effort to determine if there was any correlation between the different rut-measuring methods, a number of experiments were conducted. Three methods -- (a) South Dakota road profiler, (b) PASCO, and (c) manual -- were compared for a 7.5-mi stretch of FA 409 (US-50) in St. Clair and Clinton counties; the road profiler and manual methods were compared for all of the Interstate highways in District 5, located in east-central Illinois. In addition, the procedures used by each method were analysed to theoretically determine how well the methods would agree and also to help explain any observed differences in the data. On the basis of the results of these experiments, recommendations were made describing the most appropriate use of the road profiler data.
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