Defining threshold values for pavement surface characteristics

In the context of a rational road management strategy, pavement surface characteristics, which significantly affect comfort and safety, have to be adequately monitored and appraised in the frame of routine or preventive maintenance activities. Pavement characteristics are commonly monitored by the use of appropriate devices and evaluated by the assessment method in force. Equipment and methods may vary from one country to another or even from one highway agency to another. Undeniably, the recently elaborated and published European norms provide a reliable basis for identifying pavement properties. There still remains, however, the major issue of threshold values of pavement characteristics, which indicate the performance requirements to be fulfilled at each stage of a road's lifetime. Moreover, this issue arises not only at the operational stage of a road but also much earlier, upon completion of construction. In this paper, a systematic approach for minimum requirements of pavement condition at the initial stage of a road's lifetime is presented and threshold values of pavement characteristics are introduced. The roadway structure is represented by three major components (skid resistance, evenness, rutting) that illustrate the overall pavement surface condition. At the ‘opening to traffic' stage, the road authority or operator should specify suitable values for these pavement characteristics and this is an important issue that raises various questions. How can one define these values at the very beginning of a road's lifetime when the overall condition is practically perfect? What may be the beneficial input of effectively defining these threshold values to the highway operator? The main concept presented here is to proceed to maintenance operations once all three pavement characteristics drop below limit acceptance values. The establishment of acceptance criteria for these characteristics at the operational stage of the road and the formulation of adequate relationships for the development of pavement condition under traffic then lead to initial requirements of threshold values for the sideways force coefficient (skid resistance) and international roughness index (evenness) for main and secondary networks.