Document Type


Publication Date



Associated Schools of Construction

Source Publication

Proceedings of the 55th Annual Conference of the Associated Schools of Construction


Design-Bid-Build infrastructure projects with Unit-Price Contracts have a high risk of quantity and price deviations. Those deviations might be the result of contractors' unbalanced bidding. At the same time, contractors' performance was unknown under unbalanced bidding situations. The researchers utilized the First Order Reliability Method and Statistical Analysis to evaluate contractors' bidding performances and engineers' estimating performances with bidding and settlement data of 163 NDDOT projects. Results showed that contractors adopted unbalanced bidding strategies as follows: if quantities were overestimated, then they underrated unit price; if quantities were underestimated, then they overrated unit price to maintain projects' Bid Total Amount slightly less than Estimated Total Cost. Contractors had a 49% probability of failure in unbalanced bidding. Engineers had an 83% probability of failure in quantities overestimated and 15% in quantities underestimated. Among the estimating uncertainties, Design Errors or Changes were the main reasons of engineers' overestimating failure. The researchers recommend the use of cooperating project delivery methods such as design-build to protect owners' interests in infrastructure projects. In addition, engineers should improve their estimating accuracy by reducing design errors or changes. These research findings will help to reduce unbalanced bidding practice in public funded infrastructure projects.


Published version. Proceedings of the 55th Annual Conference of the Associated Schools of Construction, (April 10-13, 2019): 687-694. Publisher link. © 2019 Associated Schools of Construction. Used with permission

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