Estimating cost for transportation tunnel projects: A systematic literature review

Estimating the cost of transportation tunnel projects during the feasibility stage is highly complex and challenging for state/federal agencies. The use of traditional methods to estimate tunnel project costs has led to significant cost underestimation because of limited information/data to compare different alternatives. To address cost underestimation, 40 cost estimating factors were identified by conducting a systematic literature review. Seven electronic databases were searched and articles were screened based on pre-established criteria. Of the 788 articles retrieved, 39 articles published from 1988 to 2013 met the inclusion criteria and were included in the review. The resulting data was analysed using descriptive and Anderson-Darling statistical methods. The results of the analysis showed that the top five factors contributing to cost underestimation were engineering and construction complexities, geological conditions, cost estimation, market conditions, and environmental requirements. The findings from the review showed the importance of incorporating the effect of each determined estimating factor by state/federal agencies or metropolitan planning organizations when preparing initial estimates to avoid cost underestimation and/or to reduce the errors associated with such estimates. Future research may be warranted to explore the possibility of weighting the factors.