Browsing by Author "Eustace, Deogratias"

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    Appraisal of road investment strategies in Tanzania
    (University of Dar es Salaam, 1997) Eustace, Deogratias
    Feasibility studies in Tanzania suffer from lack of uniform methodology that makes comparison and ranking of different road projects a difficult task. The aim of this research in to isolate the major input parameters of the evaluation methodologies currently in use. The parameters in be investigated are those which affect the costs/benefits of the road economic evaluation, and recommendations will be made for a framework which will minimize the variation in outputs of economic evaluation due to the variations in inputs. Road economic studies in Tanzania started shortly after independence in the early 60’s and the procedures used in those early studies differ significantly from the ones being used nowadays. One of the major differences is that in the early studies, it was common to evaluate a single design alternative based upon simplified assumptions of maintenance and vehicle operating costs while the current practice include realistic models of road deterioration and relate the road condition to the costs and benefits of a road as well as specific policy alternatives available to the decision maker. Two road sections, one, paved and the other unpaved, were selected from the trunk road network for this study. A field survey was conducted for both roads which included traffic counts, axle load and roughness measurements, dynamic cone penetrometer (DCP) operations and visual surveys. Vehicle operating costs (VOC) data was collected from main transporters and vehicle dealers in Dar es Salaam. Maintenance and construction costs were obtained from the Ministry of Works (MoW) and Mwananchi Engineering and Construction Company Limited (MECCO). Economic studies were carried out using two models specially designed for road investment projects appraisal in developing counties, namely HDM-Q and RTM3. The variability of data inputs by different consultants engaged in recent feasibility studies was found to range between 0-900%. Due to the high variability of data, it was decided to perform sensitivity analyses by increasing the input data by 1005 or other appropriate increments and observe the resulting differences caused to the benefits. When an input variable was being treated, all other inputs were held constant at their base values. After running the models, the percentage change in benefits (NPV/IRR) due to 100% change or other appropriate increment in a particular input was calculated. The sensitivity analyses show that in input parameter has different effect to the output of the road economic analysis depending on the maintenance strategy adopted. Most of the parameters found to be important in one model have also been found to be important to the other model too. However, few important parameters in one model have been found to be either less important or redundant in the other. About 28 sensitive model input parameters have been identified for paved road option and 22 for unpaved road. The procedure to be used in collecting and estimation of sensitive inputs for road economic study is outlined. A general framework methodology of treating the sensitive model inputs with the aim of standardizing the procedure is also proposed.