Analysing effect of roadway width on skid resistance of porous pavement

The skid resistance available in different lanes of a multi-lane highway on a rainy day would vary because of the differences in surface run-off water thickness. This could happen on porous pavement surfaces when the rainfall intensity is high or when clogging of the porous surface layer occurs. This study presents an analytical numerical approach to analyse the relationship between the width of roadway and the skid resistance benefit of porous pavement. The analysis framework consists of a water-film thickness computation module and a skid resistance simulation model. An example case analysis is presented to illustrate the concept and framework of skid number computation for the analysis of skid resistance variations on porous asphalt surfaces of different pavement widths. The simulation results demonstrate how porous pavement skid resistance would vary with pavement width under the influence of rainfall intensity and vehicle speed. It highlights skid resistance variations with road pavement width that deserve attention in practical design of porous asphalt pavements for multi-lane highways. The skid resistance of an outer lane is always lower than an inner lane. The wider the pavement width, the larger is the difference between the skid resistance in the innermost and the outermost lane. The example problem also shows that, under the normal highway operating conditions, further losses of skid resistance in lanes beyond lane 3 are relatively small. For rainfall intensity higher than 200 mm/h, the additional losses in skid resistance in any lane would also be relatively small from a practical point of view.