Impact of Design Flaws on Cost Overruns in Road Construction Projects in Uganda

摘要

Cost overruns have remained a major setback in implementation of road construction projects worldwide. In the Ugandan construction industry, some projects have had cost overruns to a tune of 100% and are partly attributed to design flaws. This study identified major design flaws encountered during the construction phase of paved road projects in Uganda and developed a model for predicting their impact on cost overruns. A total of 37 design flaws encountered during construction were identified from literature and a questionnaire survey was conducted to establish the major design flaws based on importance index, by rating the frequency of occurrence of design flaws and their impact on cost. The effect of the five top ranked design flaws on cost overruns was established from sixteen case study projects. A regression model for predicting impact of the design flaws was developed and validated using fresh data from five projects. Results indicated the five top ranked design flaws to be: provision of less number of drainage culverts, inadequate quarries and earthen materials investigations, inadequate geotechnical investigations for road subgrade, under estimation of quantities of rock fill and provision of less volumes of cut and fill. The effect of the major design flaws on cost overrun was established to be 33.3% on average with rock fill having the biggest effect (average of 11.0%) and drainage culverts having the least effect (average of 6.7%). It was concluded that most of the design flaws which greatly affect cost overruns are attributed to non-comprehensive geotechnical and hydrological studies. It was recommended that ample time and budget be allowed for geotechnical and hydrological studies during the design stage.