Inside the Arlington Memorial Bridge, the reason for repairs that led two lanes to be closed become obvious:
Corroded steel, some that is meant to be 3/4-inch thick, now paper-thin and riddled with holes. Rusted support beams and columns. Dust from the crumbling structure that's so thick workers must wear masks.
Even the stairs are unsafe; the ones that can't be stepped on are marked with orange paint.
And then there's the question of the mechanics. "It's a drawbridge," said Jonathan Jarvis of the National Park Service. "So there's a counterweight and the whole thing pivots on basically two big axles. We don't know the structural integrity of those two big axles. They've been sitting there for almost a hundred years, rusting."
The Park Service and federal highway officials have closed two curbside lanes of the heavily traveled bridge from Northern Virginia to D.C. -- and banned tour buses from it -- to lighten the load as they make emergency repairs.
"There's no way to really evaluate what part might fail," Jarvis said. "We just look at the whole thing and know, structurally, that we need to keep heavy weight off of it."
But, with the weight limitations, drivers, bikers and pedestrians can continue to use the bridge.
"The bridge is safe, absolutely the bridge is safe," Jarvis said, "by what we've done to it, which is to move traffic to the center."
The lane closures will have to continue indefinitely. Limiting traffic on the bridge will help extend the bridge's life -- but that will also make traffic in that area even more congested.
The Park Service and Federal Highway Administration are now speeding up repairs to the bridge that had been scheduled for September.
But eventually, the entire middle section of the heavily traveled bridge will need to be replaced -- a huge project.
"I've heard it said before that in America we are great at responding to the wolf at the door, but we sometimes don't respond as well to the termites in the basement," said U.S. Transportation Secretary Anthony Foxx. "Well, today, the termites are becoming the wolf."