A FRESH LOOK AT THE INTERPRETATION OF PAVEMENT SERVICEABILITY AND AN EXPERIMENT TO MEASURE THE RIDING QUALITY OF ROADS IN SOUTH AFRICA

The need has arisen in South Africa for evaluating the condition of pavements in a systematic manner in order that maintenance can be more effectively managed and financed. In order to make effective decisions on maintenance it is necessary not only to evaluate those aspects of pavement conditions which are functional and relate to the comfort and safety requirements of road users, but also those mechanistic aspects which relate to the structural condition of the pavement. This paper approaches the evaluation of pavement condition from a functional point of view and describes the features and contributing factors that influence the present pavement serviceability; it also suggests methods for their assessment. The term 'present serviceability' as used in the AASHO Road Test related only to the aspects of the general definition concerned with riding quality. The paper concentrates on the assessment of riding quality - a function which is important to the comfort of road users and also to their safety if the road is in a very poor condition. The formulation of the equation for the measurement of the present serviceability index (PSI) is examined by means of a step-wise regression analysis of the original data and it is shown that the inclusion of the term for cracking and patching is not significant. Where the rut depth is less than 10 mm (0.4 in.) it need not be considered when evaluating the PSI. It is concluded that the effect of rutting on safety by causing ponding of water in the wheel paths should be considered separately from the effect of rutting on the PSI. Limits for rut depth from safety considerations should be set objectively for different climatic conditions. The paper also describes the results of an experiment for evaluating methods of determining the riding quality of a pavement. A large number of sections of roads were rated subjectively by a large panel of assessors in order to determine the riding quality of each section as accurately as possible. Although the mean ratings for the roads were considered sufficiently reliable, the results of the individual raters were biased to reduce the errors that usually occur in subjective judgements; it was found, however, that this made very little difference to the mean rationgs or to their reliability. The results of correlations of the mean ratings with roughness measurements, obtained by means of the BPR Roughometer and the PCA Road Meter, and with the slope variance of the simulated CHLOE profilometer, indicated that each of these instruments can give satisfactory results. The PCA Road Meter results, however, were found to depend on the type of vehicle in which it was used. This implies that the PCA Road Meter should be calibrated against a subjective rating when it is used in different vehicles. Although this is impractical, it is shown that the PCA Road Meter can be satisfactorily calibrated against slope variance provided enough measurements are used. /Author/

  • Supplemental Notes:
    • Presented at the Third International Conference on the Structural Design of Asphalt Pavements, Grosvenor House, Park Lane, London, England, Sept. 11-15, 1972.
  • Corporate Authors:

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Divil Engineering
    Ann Arbor, MI  United States  48104

    Interrational Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104
  • Authors:
    • Curtayne, P C
    • Walker, R N
  • Conference:
  • Publication Date: 1972-9

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 776-785
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00261921
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 22 1974 12:00AM