Extent of capacity loss resulting from pavement distress

The subject of this paper is the extent of pavement distress impact on traffic capacity of uninterrupted road link sections. A capacity estimation method based on extrapolation from a fundamental diagram representing the relationship between traffic flow and density was used. This method assumes that density is a result of speed and flow on sections of the road link at capacity, and hence is not directly affected by road surface distress. This implies that the capacity shifts are entirely the result of speed changes. In a ‘without and with’ distress study at selected sites in Nigeria, the impact of road surface distress was estimated for one direction of the road link section. Capacities of the road section were estimated for three sections (‘without distress’, ‘transition’ and ‘with distress’) of the road link and it was found that capacities on ‘without distress’ and ‘with distress’ sections differed significantly. The paper concludes that a significant decrease in capacity of about 30% was found, and is attributable to road pavement distress.