Quantity-based approach to preliminary cost estimates for highway projects

The preliminary cost estimate heavily influences the fate of a transportation project, yet it can be up to an order of magnitude off the final bid amount. Poor prediction of costs in state departments of transportation can lead to less-than-optimal project selection at the front end and delays later when funding is not adequate to cover planned projects. A demonstration is made of the potential to separate quantity uncertainty from price uncertainty. If item quantities can be predicted early, then readily available unit prices can be applied to create a semidetailed preliminary estimate. Compared with the typical practice of applying a gross cost per lane mile, the proposed approach provides a more detailed basis for tracking the effects of changes during project development. This methodology is being tested for implementation by the Texas Department of Transportation.