ABSTRACT
There are two main phases to this work. The first dealt with the overlay thickness design while the second considered economic appraisal of overlay design strategies. Pavement overlay design on Kaduna - Abuja road was carried out based on elastic layer and traffic estimate theories, as well as field and -Laboratory observations. The road was statistically divided into 8 homogenous sections. A computer program 'LAYER 5' was developed and used for the calculation of horizontal and vertical strain, vertical stress and fatigue remaining life of the pavement based on Odemark, Burminster and Boussinesq equations. The economic appraisal of the design was based on a cost model that considers all costs incurred over a period of 20 years. A total of 10 strategies involving design periods ranging from 2 years to 20 years at an incremental rate of 2 years were considered for the different thicknesses of the overlays. Relationships were developed for both the maintenance and users costs as functions of overlay thickness and design period. All cost items were subjected to sensitivity analyses. (vi) The results of the economic appraisals showed that those strategies that require frequent overlays are more expensive than these with fewer overlays. However, differences in total costs diminish as from the design period of 14 years onwards. Also, it was found that on the basis of present physical conditions of the road, the stretch spanning 2,3km - 8.0 km from Kaduna is the strongest.