Field Evaluation of Method for Rating Unsurfaced Road Conditions

Research was conducted to evaluate the performance of a method for rating the surface condition of low-volume unsurfaced roads and eventually to adapt the method to the situation prevailing in the state of São Paulo, Brazil. The rating method selected as the basis for this experiment is the unsurfaced road condition index (URCI) developed by the U.S. Army Corps of Engineers. The field research comprised subjective evaluations and URCI determinations performed by a rating panel composed of seven members. Some of the main questions underlying the research are: Are the original URCI deduct values curves adequate for the south Brazilian region? If not, is it possible to construct deduct values curves similar to URCI’s? To what extent can a rating panel be used to construct and calibrate these curves? Five unsurfaced county roads were selected according to the criteria of maximum soil and conditions variability. From these roads 14 segments 300 m length were selected and divided into 140 sample units 30 m in length. The rating panel attributed scores for the section, for each sample unit, and for each distress found in the sample unit. It was concluded that the panel scores for distress and surface condition of sample unit and section do not agree with the URCI computed by the method and that there is some coherence between the subjective scores given to the sample units and the score given to the section composed of these sample units.