Two Decades of Performance Comparisons for Design-Build, Construction Manager at Risk, and Design-Bid-Build: Quantitative Analysis of the State of Knowledge on Project Cost, Schedule, and Quality

Measuring the performance of design build (DB), construction manager at risk (CMR), and design-bid-build (DBB) delivery methods has been the subject of many construction research studies. The collective results of these studies are difficult to interpret because the studies extend over decades and some show mixed results as to which delivery method offers superior performance. This paper analyzes the current literature on the three most widely used project delivery methods, and combines the quantitative findings for five performance metrics: cost growth, unit cost, schedule growth, delivery speed, and quality. By combining these results, this paper considers a much larger data set of projects, which leads to more representative results and further confidence in the conclusions. The quantitative results from 30 existing studies representing 4,623 projects are combined, their methodologies are compared and contrasted, and are ordered chronologically to highlight temporal trends. Combining the results from current literature and weighting the findings using each study's sample size shows that DB is the most effective in controlling cost growth (+2.8%) as compared with CMR (+5.8%) or DBB (+5.1%). No single delivery method consistently performs better on unit cost. CMR and DB were found to be the most accurate in controlling the schedule variation of a project, with an average schedule growth of +10.2 and +10.7%, respectively, as compared with a much higher +18.4% for DBB. Moreover, DB was found to be superior in delivery speed in all explored studies and continues to increase its advantage over time. The study also highlights methodological inconsistencies in the construction literature, which could be standardized to provide more comparable results among future studies. This paper contributes to the body of knowledge by analyzing two decades of project delivery systems literature to compare the cost, schedule, and quality performance of DB, CMR, and DBB delivery systems.