Road roughness testing in Kentucky was first reported in 1949 (1). At that time, emphasis was placed on localized irregularities in pavement profiles detectable by a roller-type straight edge. The experience gained then pointed to the necessity for making a fast, continuous recording of characteristics of the road which would be more closely related to riding quality. Subsequent progress reports (2)(3) dealing with the development of triaxial acceleration as applied to the evaluation of pavement riding qualities emphasized riding comfort or discomfort. The accelerations monitored then were evaluated in terms of g's per seconds or "jerk", which is considered by some authorities to be a more significant index of comfort. This earlier method of analysis was later reviewed, and the resultant report (4) in 1961, of which this report is a continuation, considered acceleration in g's to be the most practical parameter to use in describing pavement roughness. However, only the accelerations in the vertical direction are considered in the present method of analysis. The previous reports contain descriptions of instruments and methods of recording roughness and of determining roughness indexes.

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No. 179

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