Quantitative assessment of cost and schedule goals for transportation infrastructure design-build vs design-bid-build selection criteria

Purpose The choice of design-build (DB) or design-bid-build (DBB) as a project delivery method (PDM) is increasingly important in the infrastructure space as agencies gain authority to use alternative delivery methods and expand their DB experience. There is increasing consensus in the literature that DB has an advantage in schedule performance, while findings are inconclusive for cost performance. However, delivery method selection for individual projects requires a more granular review of project goals and characteristics and their interplay with each method. To provide such a detailed perspective, this study compares quantitative cost and schedule goal assessments for pertinent PDM selection criteria. Design/methodology/approach To meet the research objectives, this study employed a two-stage approach. First, a literature review and semi-structured interviews analyzed through grounded theory were employed to finalize the criteria addressed in this work. As a result, 19 criteria, categorized into inherent project characteristics and risks, against achieving three distinct goals – lower capital cost, higher cost predictability and higher schedule predictability were included in this study. Second, 22 experts from the industry, the Texas Department of Transportation and the Federal Highway Administration provided impact assessments across the DB and DBB methods. Results were analyzed using utility theory and statistical significance tests. Findings Results indicate statistically significant differences between cost- and schedule-related impacts. For most criteria, DB selection supports achieving higher schedule predictability, while DBB selection positively impacts the higher cost predictability and lower capital cost goals. This finding provides quantitative evidence for the cost-schedule tradeoffs at the selection stage. In addition, this study provides quantitative support that project risks negatively impact both DB and DBB selection. Interaction with railroads and availability of qualified contractors presented significant differences between the two methods, contradicting the notion that DB is a vehicle for risk transfer. Originality/value This work is the first to provide detailed impacts and comparisons across cost and schedule goals during the PDM selection stage, offering insights into decision-making and risk for transportation owners. Researchers can utilize the findings of this work for further comparisons among methods and additional performance goals. In addition, practitioners from state highway agencies can use the findings to make more informed decisions about the PDM selection process for transportation infrastructure projects.