What showed during the 5.8-magnitude quake that shook much of the East Coast on Tuesday was that evacuating during an emergency could tax the city's resources.
Traffic was snarled for miles in downtown Washington as employers released workers early at the same time thousands of commuters tried to drive home or cram onto buses and trains already overloaded and slowed by speed restrictions because of the quake.
"Not that yesterday was chaos, but definitely, it was not as smooth as it could have been," said Justin Thorp, 27, a marketing manager who works downtown and who escaped the congestion with a bicycle he found through a bike-sharing program.
A strong evacuation plan is seen as especially critical for Washington, the seat of federal government and a city perpetually on guard against terrorist attacks. The president and vice president and their families enjoy Secret Service protection, and Congress has security procedures to evacuate its members. Others would have to rely on the city.
A 2006 federal government report criticized the Washington region's emergency response plan as "not sufficient" for a catastrophic incident. The most recent response plan, dated 2008, calls for the city to erect shelters and says it may be preferable for people to stay put instead of trying to evacuate.
"Human beings have a propensity to take flight rather than just to stay where they are, which is a prudent decision in a lot of situations," D.C. Mayor Vincent Gray said Wednesday.
On Tuesday, some traffic lights malfunctioned and several streets closed as crews surveyed damage. Drivers honked and trudged their way through the gridlock.
The experience was reminiscent, if not nearly as tortuous, as a January snowstorm that stranded some motorists for 12 hours or more. And as Hurricane Irene snakes up the East Coast in the coming days, the slow going also raises questions about Washington's capability to carry out a swift and efficient evacuation in the event of a full-blown disaster.
Lauren Fogg, 23, got out of work early but decided to stay to wait out the commute. She called the reaction to the earthquake "pandemonium."
"D.C., despite being super prepared, isn't," Fogg said Tuesday evening while walking with a friend on Pennsylvania Avenue.
No mandatory evacuation order came Tuesday, not surprising given the sporadic damage the city sustained.
Very few circumstances would trigger an exodus of the entire city, said David Robertson, executive director of the Metropolitan Washington Council of Governments, an organization of Washington-area local governments.
Nonetheless, many office buildings, government agencies and other businesses emptied on their own, setting off an early rush hour.
D.C. officials say gridlock is unavoidable when workers choose to leave en masse, and infrastructure improvements alone - such as building more bridges - aren't a permanent fix.
The 19 primary evacuation routes are jammed in rush hour even on an ordinary day. And in a city of not quite 70 square miles, the weekday population triples from 600,000 to 1.8 million because of workers - an influx that strains the transportation infrastructure.
"Our population goes up 1.2 million every day, so technically, we evacuate every day," said D.C. Homeland Security Director Millicent West. "The transportation system is fragile on a good day, but we are able to move people out in an orderly fashion."
Officials say they compensated Tuesday by dispatching extra police officers to work traffic control and by enacting rush hour train service about three hours ahead of schedule. Traffic lights on key outbound thoroughfares stayed green for far longer than usual. Carpool lane restrictions were lifted on highways in northern Virginia.
Officials also say the government alone is not responsible for a smooth evacuation. They say commuters should know their own alternate ride home - a link on the D.C. government website allows users to type in their address and identify the quickest path out.
And they say employers should be responsible for staggering departure times.
The mayor and West, the D.C. homeland security director, said better regional cooperation and more consistent public outreach would increase the possibility of a smooth evacuation.
The Metro Transit system, which handles more than 1 million bus and rail passengers daily in the Washington area, activated additional trains and every available operator to accommodate a rush hour that began about three hours ahead of schedule. Commuters packed downtown rail stations and trains themselves were restricted to 15 mph so the operators would have sufficient time to brake if they encountered a problem because of quake damage.
Thorp said he was concerned about how the city would cope with an actual disaster, but that mass crowds are a simple fact of life in D.C. He also questioned whether transportation headaches experienced in D.C. were really unique to this city.
"Whether it's walking or driving, taking public transit, whether it's the bus or the subway, I doubt any of them could handle all of the population trying to get home in the event of an emergency," Thorp said.
Associated Press writers Jessica Gresko and Ben Nuckols contributed to this report.