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

BMM2002-10 Topic Summary
BMM2002 10

Overview

This study, sponsored by the National Institute of Standards and Technology (NIST), was designed to provide answers to two questions by comparing the performance of owner and contractor-submitted capital projects that used one of two project delivery methods: design-build (DB) and design-bid-build (DBB). 
  • What is the relationship between capital facility project performance and the project delivery system utilized to execute it? 
  • Does the project delivery system affect safety performance? 
Some key statistics of the study data set includes:
  • Among owners, the use of the DBB delivery system dominated with nearly 75% of the projects having used it. 
  • Among contractors, the proportions represented by each of the delivery systems were more evenly split: slightly more than 56% of the projects used DBB and almost 44% used DB. 
  • Larger projects tended to use DB more often. For projects costing more than $50 million, DB represented about 47% for owners and nearly 79% for contractors.
Study results show:
  • On average DB projects were about four times larger than DBB projects in terms of project cost. 
  • Public sector projects made less use of the DB project delivery system than private sector projects. 
  • Industrial projects made greater use of DB than did building projects. 
  • Overall, owner-submitted DB projects outperformed DBB projects in cost, schedule, changes, rework, and practice use, although statistically significant differences were found only for schedule, changes, rework, and practice use. 
  • Contractor-submitted DB projects overall outperformed DBB projects in changes, rework, and practice use, but the difference was statistically significant only for change performance. 
  • Contractor-submitted DBB projects overall outperformed DB projects in schedule, and the difference was statistically significant.

For this study, the practices analyzed were pre-project planning, constructability, project change management, design/information technology, team building, and zero accident techniques.  Results include:
  • Pre-project planning and project change management practice use had the greatest impacts on cost performance for owner-submitted DB and DBB projects. 
  • Team building practice use had the greatest schedule performance impact on owner-submitted DB projects. 
  • Project change management and team building practice use had the greatest impacts on contractor-submitted DB project performance. Project change management occurred most frequently as the practice that had the greatest performance impact among contractor-submitted DBB projects. 

Key Findings and Implementation Tools

1 : Performance and Practice Use Comparison

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. 
Reference: (BMM2002-10)

2 : Owner Performance and Practice Use

Overall observed differences for owner submitted projects include:  (BMM2002-10, p40)
  • 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
Reference: (BMM2002-10)

3 : Contractor Performance and Practices Use

Overall observed differences for contractor submitted projects include:  (BMM2002-10, p40)
  • No observed 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
Reference: (BMM2002-10)

4 : Practice Use and 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.
For Owners sample of key results include: (BMM2002-10, p 53)
  • 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 sample of key results include:
  • 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. 
Reference: (BMM2002-10)

5 : Safety 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) 
Reference: (BMM2002-10)
BMM2002-10

Key Performance Indicators

Improved cost, Improved schedule, Improved quality, Improved safety, Reduced change, Reduced project growth

Research Publications

Measuring the Impacts of the Delivery System on Project Performance -- Design-Build and Design-Bid-B - BMM2002-10

Publication Date: 11/2002 Type: Benchmarking Report Pages: 97 Status: Tool


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