Cost overruns and late completion times in large infrastructure projects have been widely recognized as risks impacting project performance (Flyvbjerg et al. 2002). Controlling project budgets over project construction life cycle for mega infrastructure projects is a major challenge for both the public and the private sectors. Accurately estimating cost is an important factor for a successful project cost management from the start of planning phase to the completion of construction (Akintoye and MacLeod 1997; Nassar et al. 2005). Contingency has been used to manage uncertainty and risk in construction projects. To adequately calculate the project contingency, planners should focus on analyzing the potential risk drivers. Contingency amount is greatest in the beginning of a project and is gradually reduced as the project is designed, risks are resolved, or the contingency amount is spent (Ashley et al. 2006).