Evaluating design-bid-build and design-build delivery methods based on scope definition and differing site conditions

Abstract

There has been considerable literature written on the benefits of design-build (DB) project delivery method. Numerous research on this topic compared design-bid-build (DBB) to design-build based on cost and time, but little has been written to evaluate both delivery methods based on scope definition and differing site conditions. This research sought to investigate scope definition change orders and differing site condition change orders on Washington State Department of Transportation (WSDOT) design-bid-build and design-build projects. This research quantitatively analyzed if significant differences exist and if such differences are statistically significant enough to be attributed to the project delivery methods used. The research used available data from WSDOT on projects completed from 2002 to 2016. There were 1813 new design-bid-build projects and only 28 new design-build projects completed within this period with the first design-build project awarded in 2002 for the Sr 16, New Tacoma Narrows Bridge awarded for $615M. This paper presents a snapshot of the state of design-bid-build and design-build delivery methods at WSDOT from 2002 to 2016. Based on the data analyzed for this research, there were no significant differences in the two project delivery methods considering contract changes related to scope definition and differing site conditions. Keywords Project delivery methods Differing site conditions Contract change orders