Terrorism experts applauded the District yesterday for testing downtown emergency evacuation routes, even as they cautioned that the benefits of such exercises are limited.

Hundreds of thousands of revelers on the Mall for Monday's Fourth of July fireworks display participated in a 45-minute test, in which police steered them to seven downtown evacuation routes after the show ended.

"There is a lot of artificiality," said David Heyman, director of the homeland security program for the Center for Strategic and International Studies, a District-based not-for-profit research group. "What they could really test is the ability of law enforcement to change and control the flow of traffic. But it can't test what you really need to test -- the ability to maintain an orderly evacuation in a chaotic and fearful circumstance."

Moreover, Heyman said, the test measured the District's ability to steer people in a mass gathering, not the tens of thousands of people who on a typical workday are in office buildings spread across downtown.

"You had hundreds of thousands of people [in one place] . . . and leisurely seeking to evacuate an area over a period of time," he said. "In a terrorist attack, everyone would be distributed throughout the city, and [they] would be seeking to evacuate under stressful and emergency circumstances."

Overall, District officials said, police were able to clear the area smoothly, although they pinpointed isolated problems, such as traffic frozen as long as 20 minutes while crowds of pedestrians crossed Constitution Avenue between 12th and 15th streets NW.

"This was a very positive thing," said Edward D. Reiskin, deputy mayor in charge of public safety and justice. "People got out better and more efficiently. . . . At the same time, we learned a lot that is going to help us refine and improve."

Those who were part of the crowd gave a mixed assessment of the evacuation exercise.

Once the exercise began, some in the crowd said, they were able to walk out of the Mall easily; others described being held up by long lines that funneled them between security fencing.

"It was horrible," said Ralph Bernstein, 35, of Columbia Heights, who estimated that he waited as long as a half-hour in a line near the Vietnam Veterans Memorial.

"If there was something really going on, people would be dead," he said.

Deborah Schmitt, 50, an insurance broker from Catonsville who attended the celebration with her husband and daughter, said they encountered no lines as they left the Mall near Seventh Street NW. Their problem was finding a Metro station. "There were no signs telling which way to evacuate, this way to the bus or the Metro," she said, adding that they finally found the station in Chinatown.

Heyman and other terrorist experts stressed that simulating an emergency is problematic, if only because government agencies can go only so far in disrupting people's lives. But, they said, the tests can teach agencies how to coordinate movements and communications.

"The notion that they're thinking about it -- and testing it -- is very positive, rather than other cities that leave it up in the air," said John Sorenson, a researcher at Oak Ridge National Laboratory in Tennessee who studies how people respond to emergencies.

Dan Tangherlini, director of the District's Department of Transportation, which coordinated the test, acknowledged that it was limited because it did not simulate emergency conditions.

"What we have been doing in the way of testing is war-gaming stuff and talking it through," he said. "Here we tried some of this stuff. You can point to all the things that weren't consistent with an emergency, but there are things that were -- in terms of the volume, the constrained time period and the focus on egress."

D.C. Transportation Department officials used traffic cameras to monitor the experiment. Shown are, from left, Natalie Jones Best, Michelle Pourciau and Bill Rice.

Thomas Lockwood, right, director of national capital region coordination for the U.S. Department of Homeland Security, confers with Edward D. Reiskin, deputy mayor for public safety, during the exercise.

Densely packed crowds of people leave the Mall after the Fourth of July fireworks show.