Human judgement and analytical derivation of ride quality

Questions concerning when a road ceases to serve the public well or has failed are closely related to the ride quality of the road. The quantification of the rideability or serviceability of road deals with the human rating of ride quality. For the most thorough rating, a select panel of raters has been used to rate a road section after having either driven or ridden over the section. The average of the ratings may be called the present serviceability rating (PSR). Given a set of PSR covering a wide spectrum of roads of different surface characteristics, the essential question is how to explain the PSR in terms of the explanatory variables describing human sensitivity in some relevant functional form. It is apparent that a rater responds to the vibration environment in a moving vehicle induced by the longitudinal roughness of a road. This paper presents an analytical model connecting the characteristics of a road profile, and the dynamic response of a vehicle to the profile, to the human ratings of the ride quality. Analytical expressions for various dynamic indices in a moving vehicle are derived. Very good agreement between the model prediction and the ratings is demonstrated using actual field data. Obtaining a good model prediction would give the means of obtaining a rating of road quality comparable to that provided by experts, without the associated expense of employing such experts.