Measuring the Impacts of the Delivery System on Project Performance -- Design-Build and Design-Bid-B

Table ES.1 below, summarizes the overall results, indicating the better performing delivery for six metric categories (BMM 2002-10, p. ix):

• Owners – There seemed to be a performance advantage when the DB delivery system was used.
• Contractors – The performance advantage for one delivery system over the other was not as clear.

Practice use seemed to be a driver of performance results as much as project delivery system. No one project delivery system is likely to provide the best performance for all projects and for all participants.

Overall observed differences for owner-submitted projects include (BMM2002-10, p. 40):

• Cost performance was better for DB projects than it was for DBB projects.
• Projects using DB consistently demonstrated better schedule performance. 
• For changes, rework, and practice use, DB projects clearly had the advantage over DBB projects
• For industrial projects, DBB projects had better safety performance.

Overall observed differences for contractor-submitted projects include (BMM2002-10, p. 40):

• No difference in cost performance was observed between DB and DBB projects.
• Projects using DBB achieved better schedule performance than project using DB.
• For changes, rework, and practice use, DB projects usually outperformed DBB projects.
• Neither delivery system dominated the other in regard to safety performance.

It was generally found that projects with higher practice use scores also tended to have better performance outcomes. Some practices were more likely than others to be associated with better performance, however (BMM2002-10, p. 53).

For owners, a sample of key results includes:

• The use of the DB delivery system tended to yield better performance outcomes for owner-submitted projects; these projects tended to have better performance in cost, schedule, changes, rework, and practice use.
• Pre-project planning and project change management provided the greatest benefit in cost performance.

For contractors, a sample of key results includes:

• DBB projects outperformed DB projects in schedule, but contractor-submitted DB projects had better performance in changes, rework, and practice use.
• Pre-project planning and project change management provided the greatest benefit in cost performance.

Safety incentive use seemed to have a notable influence on safety performance between DB and DBB projects. Contrary to expectations, fast tracked owner-submitted DBB projects had better safety performance than non-fast tracked DBB projects. Likewise, behind schedule owner-submitted DB projects had better safety performance than either ahead of schedule or on-time DB projects. Preliminary investigation showed that these projects also made greater use of safety contract incentives. As expected, ahead of schedule owner and contractor-submitted DBB projects had better safety performance than either on time or behind schedule projects (BMM2002-10, p. 49).