Climate Change and Its Impact on U.S. Transportation

The committee that wrote the report, which included experts in climate science, geology, risk assessment, transportation planning and engineering, and infrastructure, agreed unanimously that climate change will have a significant impact on transportation infrastructure and operations. "Now is the time to pinpoint vulnerabilities and incorporate present scientific knowledge into the planning, design, construction, operation, and maintenance of transportation systems," said Henry Schwartz Jr., chair of the committee that wrote the report.

Every mode of transportation in the U.S. will be affected as the climate warms, but potentially the greatest impact will be flooding of roads, railways, transit systems, and airport runways in coastal areas because of rising sea levels and surges brought on by storms. Some 60,000 miles of coastal highways are already exposed to periodic storm flooding, and erosion and loss of wetlands have removed crucial buffer zones that once protected many roads.

The U.S. transportation system was designed and built for typical local weather and climate, assuming a reasonable range of temperatures and precipitation levels based on historical data. The report finds that these data may no longer be a reliable guide for transportation planners, however, as warming temperatures trigger new weather and climate extremes. Infrastructure pushed beyond the range for which it was designed can become stressed and fail, as seen with the loss of the U.S. 90 Biloxi Bay Bridge after Hurricane Katrina.

The next 50 to 100 years will see increases in very hot days and heat waves, increases in Arctic temperatures, sea-level rise coupled with storm surges and land subsidence, more frequent intense precipitation events, and increases in the intensity of strong hurricanes. And the impacts of some of these changes will extend well beyond coastal areas. In the Midwest, for instance, increased intense precipitation could augment the severity of flooding as occurred in the "Great Flood" of 1993 that damaged farmland, towns, and transportation routes along 500 miles of the Mississippi and Missouri river systems. On the other hand, drier conditions are likely to prevail in the watersheds supplying the St. Lawrence Seaway, Great Lakes, and Upper Midwest river system. Lower water levels would reduce vessel shipping capacity, seriously impairing freight movement in the region. And in California, heat waves may increase wildfires that can destroy transportation infrastructure.

Not all climate changes will be negative, though. Marine transportation could benefit from more open seas in the Arctic, creating new and shorter shipping routes and reducing transport time and costs. In cold regions, warming temperatures could reduce the costs of snow and ice control, making travel conditions safer for passenger vehicles and freight.

The report calls for a concerted federal role in implementing many of its recommendations such as creation of an information clearinghouse on transportation and climate change, establishment of a research program to re-evaluate design standards in light of climate change, creation of an interagency working group on adaptation, and re-evaluation of the National Flood Insurance Program.

Many of the recommendations need not wait for federal action, the committee said. Local governments and private infrastructure providers can begin to identify critical infrastructure particularly vulnerable to climate change. Professional organizations can single out examples of good adaptation practices, and transportation planners and climate scientists can begin collaborating on the development of regional scenarios for likely climate-related changes and collection of data needed to analyze their impacts.

Focusing on the problem now should help avoid costly future transportation investments and disruptions to operations.   -- Maureen O'Leary

Potential Impacts of Climate Change on U.S. Transportation. Committee on Climate Change and U.S. Transportation, Transportation Research Board and Division on Earth and Life Studies (2008, approx. 234 pp.; ISBN 0-309-11306-7; available from the National Academies Press, tel. 1-800-624-6242; $37.00 plus $4.50 shipping for single copies).

Henry Schwartz Jr., past president and chairman of Sverdrup/Jacobs Civil Inc., chaired the committee. The study was funded by the Transportation Research Board; National Cooperative Highway Research Program; U.S. Department of Transportation; Transit Cooperative Research Program; U.S. Environmental Protection Agency; and the U.S. Army Corps of Engineers.