Life-cycle cost comparison of alternative surfacing for steep slopes on low-volume roads in Ghana

Abstract

teep hill sections of low-volume (i.e. feeder) roads in Ghana are at high risk of slope failure, erosion, and drainage-related problems that ultimately affect the rural communities in respect of traffic delays, safety, damage to natural resources, and economic activities. These problems have been mainly attributed to prolonged rainy seasons, coupled with weak natural (lateritic) soils that are commonly used as wearing course on the feeder roads. A study was recently conducted to identify alternative surfacing options to gravel wearing courses used on steep gradients (in excess of 12%) of feeder roads in Ghana. A major outcome was three surfacing options (i.e. concrete, bituminous and stone setts/cobbles) that would be more effective to address drainage and erosion problems on the steep section than gravel wearing courses currently used by the Department of Feeder Roads (DFR). The objective of this paper is to present a life-cycle cost comparison of six pavement options proposed for steep hilly sections of feeder roads in Ghana. The economic evaluation methodology adopted is the present worth of cost. Although not very decisively, the life-cycle cost analysis of the six pavements indicated that with a real discount rate of 12%, 70 mm ultra-thin reinforced concrete surfacing has the lowest cost (GBP 69.7/m²), whereas 50 mm hot-mix asphalt emerged as the option with the highest cost (GBP 91.7/m²). Based on the analysis results, it is concluded that all six pavement options remain cost-effective structures compared with a gravel wearing course. However, the current policies of the DFR may influence the decision on particular surfacings to be adopted for feeder roads in Ghana.