Bethesda residents fumed Thursday at the Navy's first public explanation of how its expansion plans would affect traffic around the medical center campus along Rockville Pike, accusing the military of failing to resolve the gridlock it has already helped create along the busy road.

The Navy plans to demolish five hospital buildings at Walter Reed National Military Medical Center, replacing them with a five-story building and a 500-space underground parking garage. The military also plans to add a 341,000-square-foot research facility to the Uniformed Services University of the Health Sciences campus and a 400-space parking garage for university staff, among other renovations.

The Navy's new draft study on the environmental impacts of its plans shows that the changes will add only 270 staff to the campus and 17 seconds to commuters' drive time on Rockville Pike between Grosvenor Lane and Woodmont Avenue during the morning rush hour.

But residents aren't buying the math.

"It's like a parking lot [on Rockville Pike]," said Bethesda resident Andres Buonanno. "It sounds like you're fooling around with the numbers."

Maria Morasso, also of Bethesda, agreed.

"I don't know where that number could have come from," she said.

Morasso also questioned why the Navy had no plans to improve nearby intersections, two of which -- Rockville Pike and Cedar Lane, and Jones Bridge Road and Connecticut Avenue -- the Navy graded F.

"How do we convey our frustration for you to understand that what we want is A, B, C, not failing at an F?" she said.

Marilyn Lipowski, a nearby resident and an outpatient at the National Institutes of Health across the road, said she tries to leave her NIH appointments before noon because she can't pull out on Rockville Pike in the afternoon.

"It's bumper-to-bumper. And that's during the day, not at rush hour," she said. "No one who works at your facility should have to take a car. You have the [Metro] train right there. ... I just thought there would be extra roads when the new buildings went up."

The site's commanding officer, Capt. Frederick Kass, said the Navy is working to relieve congestion.

"I don't own the roads around the installation. The county and the state [do] -- at the end of the day, it's their responsibility," he said. "We try to be good neighbors."

The Pentagon took heavy criticism over the past year when it consolidated the Walter Reed Army Medical Center in the District with what was then the National Naval Medical Center in Bethesda, virtually doubling the number of people working and visiting the Bethesda site without making any improvements to surrounding roads to accommodate that growth.

The Navy has reduced the number of staff driving to work by themselves from 72 percent in 2007 to 40 percent in 2011, said campus transportation manager Jeff Miller.