Tunneling Toward the Future
The United States is home to more than 300 highway tunnels. A significant number of these were constructed during the development of the interstate highway system in the 1950s and 1960s. The age of these tunnels poses numerous challenges for those responsible for inspecting, maintaining, and operating them to ensure the safety of the traveling public. For years, the Federal Highway Administration's (FHWA) tunnel program has provided technical assistance to the States in the areas of design, construction, maintenance, and operation. Program staff has worked with the American Association of State Highway and Transportation Officials (AASHTO), the Transportation Research Board, the tunnel industry, and other Federal agencies to develop guidelines and conduct research to improve the safety and security of highway tunnels.
As early as 1983, FHWA published a report presenting methods for responding to fires in highway tunnels. Prevention and Control of Highway Tunnel Fires (FHWA-RD-83-032) underscores various means of evaluating and reducing the risk of fires, as well as ways to minimize damages, injuries, and fatalities.
In 2005, FHWA, AASHTO, and the National Cooperative Highway Research Program (NCHRP) sponsored a scan of European tunnels. The objectives were to learn about international efforts regarding underground transportation systems in the areas of safety, operations, and emergency response. The resulting report contains recommendations to FHWA and AASHTO on strategies to enhance the safety, operation, and maintenance of highway tunnels.
Then, in 2009, FHWA published a Technical Manual for Design and Construction of Road Tunnels -- Civil Elements (FHWA-NHI-10-034). The manual provides guidelines and recommendations for planning, designing, constructing, and structurally rehabilitating and repairing the civil elements -- such as roadway pavement, walkways, and guard rails -- of road tunnels, including cut-and-cover, mined and bored, immersed, and jacked box tunnels.
In August and September 2009, in partnership with AASHTO and NCHRP, FHWA completed a domestic scan and follow-up report on Best Practices for Roadway Tunnel Design, Construction, Maintenance, Inspection, and Operations (NCHRP Project 20-68A, Scan 09-05). The information gathered during the domestic scan laid the foundation for a national tunnel inventory. The final report is available at www.fhwa.dot.gov/bridge/tunnel/library.htm.
All of these endeavors have contributed to FHWA's work to develop National Tunnel Inspection Standards (NTIS) modeled after the National Bridge Inspection Standards, an effort that just received an important push from Congress and President Obama. In July 2012, Congress passed and President Obama signed into law the Moving Ahead for Progress in the 21st Century Act (MAP-21). This legislation represents a critical milestone for tunnels in the United States, as it requires the Secretary of Transportation, in consultation with the States, to establish national standards for tunnel inspections. The NTIS will ensure the safety and security of the traveling public by requiring that all structural, mechanical, electrical, hydraulic, and ventilation systems, and other major elements of the Nation's tunnels, be inspected and tested on a regular basis. The NTIS also will make tunnel inspection standards consistent across the country.
Thanks to these initiatives and more, FHWA's tunnel program will continue to help States keep existing tunnels in good repair, while ensuring that new ones like the Alaskan Way Tunnel in Washington State and the Devil's Slide and fourth bore of the Caldecott Tunnel in California operate safely and effectively for years to come. For more on the Alaskan Way Tunnel project, see "From Milepost to Milestone: Innovative Mitigation" on page 20 in this issue of Public Roads. For more on the Caldecott Tunnel, see "An Eight-Lane, Four-Bore Hole in One" on page 10.
Jesus M. Rohena, P.E.
Senior Bridge Engineer - Tunnels
Federal Highway Administration