A decade after terrorists targeted the Pentagon, it is unreasonable to think that Washington can be swiftly evacuated if they strike again, evidence and experts agree.

Ironically, two acts of God this year have driven home the point that it is impossible for everyone to leave town in a hurry.

“Not only can it not be done, we should not try it,” said Ron Kirby, transportation planning coordinator for the Metropolitan Washington Council of Governments.

Ten years ago, people fled after a terrorist attack; in January, they tried to escape a particularly treacherous winter storm; and this week, they headed home en masse after an earthquake.

Each of those events provided emergency planners with a fresh template for improvement and underscored the futility of an unstructured exodus from the city.

“You can just look at the evacuations that are taking place for the hurricane that’s approaching to see that in most cases they take several days,” said Montgomery County Council member Phil Andrews, who chairs the Emergency Preparedness Council, a regional committee under the Council of Governments.

Information stream vital

No matter the event that encourages people to flee, Kirby and Andrews agree that providing the public with a steady stream of information about conditions is an essential component.

“You should never try to tell people what they ought to do, because all of their circumstances are different,” Kirby said, “but if you give them very good timely information, they are going to make their own decisions in ways, in general, that are going to be better for them and better for the system as a whole.”

Kirby, who commutes on Metro, said the Transit Authority should have provided better information. “None of us felt like we had adequate information on the service level at Metro until we were already jammed on the train,” he said.

Metro spokesman Dan Stessel said the agency released information as soon as officials knew what level of service they would be able to provide — 43 minutes after the earthquake.

“We immediately put it out to the public through every communication channel — wire services, broadcast media, Facebook, Twitter and our Web site.”

He said Metro also shared information through transportation command centers in the District, Maryland and Virginia as well as the Council of Governments.

Rail riders experienced additional delays because crews had to inspect tracks, bridges and tunnels.

Andrews said a new regional Web site that will coordinate all available transportation information in real time is expected to be up and running this year.

Despite congestion and frustration on the roads, the people who track data on the region’s traffic said that Tuesday’s back-ups were no greater than what drivers experience during a heavy rush hour. It just began early.

“Once people began moving out, it was just a volume issue,” said Taran L. Hutchinson, facilitator at the Metropolitan Area Transportation Operations Coordination center in Greenbelt.

A formal plan in works

After 9/11, people realized the importance of leaving the city quickly if terrorists unleash an attack.

Evacuation plans were formulated by business and building owners, foremost among them the region’s largest employer: the federal government.

The panel of regional officials headed by Andrews was convened to knit it all together into a plan for an orderly exodus. Its final recommendations will be made to the Council of Governments this fall.

They faced an enormous, obvious obstacle. On any good weekday, Washington traffic overwhelms road capacity at peak rush hours. If everyone were to head for home at once in an emergency, the major arteries and rail lines would not be able to handle the volume.

Planners suggested “sheltering in place,” and many offices have arranged to do that in certain circumstances, but steps also have been taken to evacuate people from the center of town.

Limited by the number of bridges to the south and east, and the handful of major arteries to Maryland, the plans call for changing traffic signals to favor outbound flow, stationing officers to speed traffic through key intersections, marshaling all available rail cars and making similar tweaks.

The need for action was hammered home last winter, when a Jan. 26 ice and snow storm caused what may have been the most crippling traffic debacle in local history. Some commuters did not get home until the next day.

The problems were a unique confluence of weather, communication issues and questionable decisions.

The finger was pointed most often at a federal decision to send government employees home early as conditions worsened.

Some were faulting the federal government again this week. Federal workers said their employers exercised elements of long-practiced emergency procedures, but several cited communication problems after a decision by individual agencies to give workers the option to leave at 2:30 p.m. The Office of Personnel Management didn’t issue its formal recommendation until 4 p.m., and most workers didn’t get an e-mail notice until 4:30. OPM determines when area federal offices should open late or close early.

“I did not feel like I knew what to do,” said Bill Samuel, who works for the Environmental Protection Agency at its headquarters on Constitution Avenue. “Many people were saying we should evacuate,” he wrote in an e-mail, “and people spontaneously evacuated EPA’s buildings at the Federal Triangle. However, no official order was ever given to the best of my knowledge.”

OPM said Wednesday that it had never conducted an earthquake-related dismissal drill.

Kirby said that after an earthquake, it would have been virtually impossible for OPM or other organizations with multiple locations to control the flow of workers heading home.

“There was really nobody in position to control demand, because the demand issue was pretty much a building-by-building decision,” he said. “There was no way that could be coordinated.”

Staff writer Dana Hedgpeth contributed to this report.