The Kenya Road Transport Cost Study: Research on Road Deterioration

This report describes a study of the performance of paved and unpaved roads which was undertaken in Kenya as part of a larger study designed to provide suitable relationlships for use in a computor model capable of estimating the construction costs, maintenance costs and road user costs throughout the life of a road in a developing country. The paved-road sample consisted of thirly-nine sections located on surface-dressed roads with cement-stabilized bases and ten sections located on asphaltic concrete roads with crushed stone bases. The unpaved-road sample consisted of thiry-eight test sections located on properly engineered gravel roads (lateritic, quartzitic, volcanic and coral) and eight sections on earth roads. The deterioration of the surface of the paved roads was quantified in terms of surface roughness, amount of cracking and depth of ruts. These parameters together with the transient deflections and the CBR and the moisture content of the various pavement layers were monitored for a period of up to four years. The deterioration of unpaved roads was quantified in terms of srface roughness, depth of ruts, depth of loose surface material and the thickness of the gravel layer. There parameters were monitored for a period of two years. The deterioration of the roads was related to the traffic loading, the original design and construction standard of the roads, the maintenance policy in use and the environmental conditions.