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.1 Although a comprehensive account of these unpredictable interruptions has not been undertaken nor data compiled on them, numerous studies and other analyses have sought to evaluate the effects of individual events on the transportation system.

In a 10-day shutdown of West Coast ports in fall 2002, members of the Pacific Maritime Association imposed a lockout in response to a perceived work slowdown by International Longshore and Warehouse Union workers. The port closure ended when the Bush Administration invoked the Taft-Hartley Act; management and the union subsequently ratified a six-year contract in January 2003. Over half of U.S. containerized merchandise trade, measured in 20-foot equivalent units (TEUs), passes through West Coast ports. With a sizeable share of this trade originating from or destined for states throughout the country, the shutdown of these ports negatively affected freight traffic nationwide. Shipments by retailers, manufacturers, automakers, and the agricultural sector were particularly impacted. Each year, imports through West Coast ports decline in late fall and resume early in the following year (figure 8-9). Because of this, the decline caused by the lockout is not readily apparent in overall containerized cargo data.

Vehicle accidents are a common cause of transportation delays. National estimates, based on model simulations, suggest that nearly 40 percent of nonrecurring delays on freeways and principal arterials are due to crashes. Weather, another unpredictable factor, accounts for 27 percent of highway delays. Relatively fewer delays resulted from road work zones (24 percent) and vehicle breakdowns (11 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 [2]. 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 [3]. 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 [4, 5]. The threat and aftermath of Hurricane Isabel in September 2003 caused the Washington (DC) Metropolitan Area Transit Authority to shut down its transit rail system for two days.


1. Chin, S.M., O. Franzese, D.L. Greene, H.L. Hwang, and R. Gibson, “Temporary Losses of Highway Capacity and Impacts on Performance,” Oak Ridge National Laboratory, May 2002.

2. 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.

3. U.S. Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics Annual Report 1994 (Washington, DC: 1994).

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

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

1 For data on the impact of the Sept. 11, 2001, terrorist attacks on U.S. domestic flight operations that month, see U.S. Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics Annual Report (October 2003) (Washington, DC: 2003).