Metaanalysis on Cost Growth Gap between DesignBuild and DesignBidBuild Projects

Abstract:

A thorough review of literature on DesignBuild (DB) and DesignBidBuild (DBB) project cost growth performance comparison indicates that existing studies focus on different types of projects, and most studies build on limited samples of projects. As a result, the conclusions of previous studies are diverse, and no general consensus has been reached on whether DB outperformed DBB in terms of cost growth. This paper employs random effect metaanalysis model to statistically integrate results in previous studies. Based on the integrated large sample, the gap between cost growth in DB and DBB projects is evaluated. The metaanalysis results, verified by the robust tests, show that DB projects achieve significantly lower cost growth on average. Further metaanalyses on different groups of studies reflect that DB system performs worse in public projects but better in unique projects. DBB is more conducive to cost growth control under complex project conditions. Cost growth improvements induced by DB system experienced growth initially, followed by shrinkage afterwards due to policy changes. This reminds clients that PDS should be selected according to specific project conditions. Hence, clients should consider both project conditions and performance history of different PDSs when selecting PDS. Clients may find this paper helpful in supporting their PDS selection decisions.

Key words:design-build system; design-bid-build system; project delivery system (PDS); cost growth performance; metaanalysis