Predicting preliminary engineering costs for bridge projects

Preliminary engineering (PE) for a highway project encompasses two efforts: planning to minimize the physical, social, and human environmental impacts of projects and engineering design to deliver the best solution. PE efforts often begin five or more years in advance of the project's actual construction. An efficient and accurate method to estimate PE costs would benefit transportation departments by facilitating funding allocation projections. Lacking an effective model to estimate PE cost based on project characteristics, departments of transportation typically estimate PE costs as a fixed percentage of estimated construction costs disregarding other project-specific parameters. Using data from 461 North Carolina Department of Transportation (NCDOT) bridge projects awarded for construction from 2001 through 2009, the authors are developing a multiple linear regression model to link variation in PE costs to a set of project variables. Data sources included bid summaries, bridge inventory and assessment reports, the NCDOT project management system, and environmental reports. Early results indicate that right-of-way costs, regional location, and scope delineators are among the project-specific parameters that have the most influence on the PE costs of bridge projects in North Carolina. By considering numerous parameters financial analysts can make more accurate predictions of PE costs for future projects than was ever possible before.