Tunneling for transit projects is as much an art as a science. Variables affecting the design and construction of a project include predicting the behavior of ground mass during construction and the vagaries of ground-water hydrology. Predictive models are only of some use because no two projects are the same. The process of tunnel design and construction involves evaluation of geologic conditions, identifying and acquiring the appropriate tunnel boring equipment, ground modification techniques, environmental impact mitigation, utility and traffic protection, contractor selection and payment, and risk management. Research is needed in all of these areas.

Many innovations have been made in tunnel technology. This information needs to be collected and reviewed to identify the range of options available to minimize the problems an initiator of a subway project may face. Lessons have been learned from projects completed in the U.S. and in other countries that should help identify ways to achieve greater efficiency in the design and construction of subway tunnels. The strong and weak aspects of tunneling methods, such as two-pass, single-pass, and the New Austrian Tunneling Method (NATM), must be identified as they relate to geological conditions, scheduling, budgeting, and functional constraints.

Federal Transit Administration (FTA) research will analyze and catalogue lessons learned and provide information to make this information available to the transportation industry in a usable format. This is a starting point for devising better design and construction processes and for developing effective risk mitigation techniques. Other research topics to be considered include assessment of tunnel infrastructure conditions and evaluation of non-destructive testing methods. Advances in thermal scanning, high resolution ultrasonic, scanning, and radar detection may have the potential to address this problem.

Related Resources

• American Public Transportation Association (APTA)
• Bay Area Rapid Transit (BART), Oakland, California - San Francisco International Airport Heavy Rail Transit Extension
• Bi-State Development Agency - St. Clair County Light Rail Transit Extension
• Central Florida Regional Transportation Authority (LYNX), Orlando, Florida - Light Rail Transit is Coming to Central Florida
• Community Transportation Association of America (CTAA)
• Dallas Area Rapid Transit (DART), Dallas, Texas - Light Rail Transit Expansion Projects
• Department of Transportation and Public Works (DTOP), San Juan, Puerto Rico - Tren Urbano Light Rail Transit Project
• Los Angeles County Metropolitan Transportation Authority (LACMTA), Los Angeles, California - Metro Construction Projects
• Metropolitan Atlanta Rapid Transit Authority (MARTA), Atlanta, Georgia - Heavy Rail Transit Design and Construction
• Metropolitan Transportation Authority (MTA), New York, New York - Capital Programs
• Regional Transit District (RTD), Denver, Colorado - New Light Rail Transit Construction Projects
• Tri-County Metropolitan Transportation District of Oregon (Tri-Met) - Westside Light Rail Transit Extension
• Utah Transit Authority (UTA), Salt Lake City, Utah  - North-South Line Light Rail Transit Construction

Contacts

Please submit questions or comments regarding Transit Research and Technology Programs to:

Director
Office of Technology, TRI-20
Federal Transit Administration
400 7th Street, SW
Washington, DC 20590
202-366-4035

Mary L. Anderson
Civil Engineer
Federal Transit Administration
400 7th Street, SW
Washington, DC 20590
202-366-0222