Intermittent Interruptions of Transportation Services

Intermittent Interruptions of Transportation Services

Natural disasters, accidents, labor disputes, terrorism, security breaches, and other incidents can result in major disruptions to the transportation system. Although comprehensive data on these interruptions are not available, numerous studies and other analyses have sought to evaluate the quantitative effects of individual events.

In the years leading up to the terrorist attacks of September 11, 2001, international passenger travel on 10 major carriers grew steadily (figure 12-8). From 1994 through 2000, the number of passengers increased 30 percent. As a result of the attacks and the economic downturn at that time, however, the trend changed and international travel decreased by over 10 percent from 2000 to 2003. By the end of 2004, 4 of the 10 carriers had recovered to pre-September 11th levels.

An unusually strong 2004 hurricane season in Florida caused a large number of flight delays and cancellations (figure 12-9). In August, Hurricane Charley struck the southwest coast of Florida.1 Three more storms hit Florida in September. First, Frances hit the east coast of the state, and then Ivan crossed Florida (affecting both the east and west coasts). Finally, Hurricane Jeanne made landfall close to where Frances had only 20 days earlier [2]. Numerous airports closed their runways during these storms. Two times in September, for instance, Orlando International Airport closed for more than a day [4]. It is difficult to determine the total number of flights that were disrupted nationally as a result of weather conditions in Florida. However, cancellations in Florida increased considerably in August and September 2004 compared with those months in 2003.

Vehicle accidents are a common, yet unpredictable, cause of transportation delays. National estimates, based on model simulations, suggest that nearly 45 percent of nonrecurring delays on freeways and principal arterials are due to nonfatal crashes. Weather, another unpredictable factor, accounts for 9 percent of highway delays. Relatively fewer delays resulted from road work zones (24 percent) and vehicle breakdowns (12 percent) [1]. Although motor vehicle accidents are, by far, the most frequent type of transportation accident, other modes also experience major disruptions due to accidents. A freight train carrying hazardous materials derailed in a Baltimore tunnel in 2001 [3]. The resulting fire lasted several days and forced the city to close some highways and rail passages. Freight and passengers were delayed as trains were diverted hundreds of miles throughout the mid-Atlantic region.

The United States , because of its size and varied geography, is vulnerable to many types of natural disasters that can affect transportation. The flooding of the Mississippi River in 1993 shut down large portions of the inland waterway system, washed out rail track, damaged rail bridges, and closed an estimated 250 highway segments and bridges [5]. The following year, the Northridge earthquake had a major impact on the Los Angeles metropolitan area transportation system. Measuring 6.8 on the Richter scale, the earthquake knocked out four freeways, caused the collapse of parking structures, and ruptured numerous natural gas distribution lines [6, 7].


1. S.M. Chin, O. Franzese, D.L. Greene, H.L. Hwang, and R. Gibson, "Temporary Losses of Highway Capacity and Impacts on Performance: Phase 2," Oak Ridge National Laboratory, 2004.

2. National Oceanic and Atmospheric Administration, National Hurricane Center,

3. National Transportation Safety Board, "Update on July 18, 2001 CSXT Derailment in Baltimore Tunnel," press release, Dec. 4, 2002, available at, as of June 2004.

4. Orlando International Airport, press releases, available at

5. U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, Transportation Statistics Annual Report 1994 (Washington, DC: 1994).

6. _____. Transportation Statistics Annual Report 1995 (Washington, DC: 1995).

7. _____. Journal of Transportation and Statistics: Special Issue on the Northridge Earthquake 1:2, May 1998.

1 This Category 4 storm was the strongest to make landfall in Florida since Hurricane Andrew in 2002.