The results showed that, on average, DB projects were delivered faster and with nominally lower cost growth and schedule growth than their CMR and DBB counterparts. The completed unit cost of DB projects was also comparable to DBB and slightly less than CMR projects. However, the modeling does indicate that, except for delivery speed, the gap in performance between DBB, CMR, and DB has narrowed over time.
By examining the regression models themselves, several other variables, in addition to the project delivery system, contributed to these performance differences. Projects with excellent team chemistry and open book contracting terms (e.g., cost plus a fee and GMP) were, on average, more likely to have lower unit costs and cost growth. On average, projects that involved both the designer and builder in early goal-setting had reduced schedule growth. These findings provide further evidence that the project delivery system is not the sole contributor to project performance and these human-related factors are, in some cases, equally as important.