Comparison of DB to DBB on highway projects in Washington State, USA

Author name(s): 
Okere, G

Comparative evaluations of design-build (DB), to design-bid-build (DBB), are documented in literature. However, a recent study suggests that even though several studies have been completed to compare DB and DBB, there are few statistically significant comparative results. Comparative analyses of highway projects of the same scope, size, and type could provide the basis to make the argument for the use of either DB or DBB on highway projects. The objective of this research is to compare DB to DBB on highway projects. The basis of comparison includes project cost, contract duration, number and type of contract change orders. Projects used for this research were obtained from the Washington State Department of Transportation (WSDOT). The projects were subsequently selected based on project scope, size, and type, and then analysed using quantitative methods. The research found that there is enough evidence to support the use of DB over DBB on highway projects. The findings of this study have significant implications for practitioners and policymakers on highway projects and should inform decisions on the choice of project delivery method. The main limitation of the research is that the study used only 14 projects due to the difficulty of finding matching projects, and as such the results could not be generalized. However, the findings add to the body of research on criteria for comparing DB to DBB. To enhance understanding of how project scope, size, and type might affect or be affected by project delivery methods, the research recommends the standardization of project types classification for highway projects.