Impallaria said the Old Mountain Road overpass, which is next to a park-and-ride lot, served as a convenient location for flag wavers, and allows "all those people commuting on I-95 to see that we haven't forgotten what happened on 9/11."
He said the event gives motorists "an opportunity to participate in the remembrance, even if it's just blowing their horns and waving."
Brian Sams, of Darlington, waved a flag with the names of "every person lost" on 9/11. He ordered the flag online.
He said he was on the overpass "to honor all of our lost citizens who perished, our veterans and soldiers who fought for our country."
LeRoy Edmunds III, of Bel Air, waved a flag while standing on top of a 1958 Ward LaFrance fire truck he had spent three years restoring with his father, LeRoy Jr.
LeRoy III is a Baltimore County career firefighter, and volunteers with Joppa-Magnolia. He noted the engine, which belonged to Ferndale's volunteer fire company bore the number 343, the number of New York firefighters killed at the World Trade Center.
He said he and his fellow Baltimore County firefighters at Station 16 became friends with firefighters in the FDNY's Engine 16/Ladder 7 after making a bet on Super Bowl XXXV, when the Baltimore Ravens defeated the New York Giants in early 2001.
Eight months later, Edmunds and other Baltimore County firefighters traveled to New York to console their grieving brothers, who lost nine of their comrades in the World Trade Center collapse.
"People were so nice to us," Edmunds told The Baltimore Sun about the trip to New York for a 2001 story. "We went into a biker bar and people clapped. Strangers on the street hugged us. We told them we weren't from New York, we were from Baltimore. And they said, `We don't care, we love you. ... You're here. You came up here to support our guys.' "
Wayne Howell, of Joppa, leaned on several large bamboo poles to which he had attached American flags.
He recalled his cousin, Steven, who was working in the World Trade Center on 9/11 and lost his life in the collapse.
Howell said his cousin was on a floor above where one of the two planes hit, and "didn't have a chance."
He said he has taken part in nearly every flag-waving event in remembrance of his cousin.
"I love it, he said. "Hopefully they understand everything that happened [on 9/11] and remember it and never forget it."