Bertha may be a dummy, but the corporal assigned to the Herndon Police Department's traffic division is getting results.

Rush-hour commuters are doing double-takes when they spot the serene, uniform-clad officer -- actually a mannequin -- in traffic hot spots throughout the town in northern Fairfax County.

Perched in the driver's seat of a police car, the dummy police officer appears to be aiming a radar gun.

Her boss, Lt. Duane Atkisson, gives top marks to Bertha, who graduated from SWAT training to traffic duty three weeks ago. "She is performing an exemplary duty," he said.

Atkisson said he borrowed the idea from the Leesburg Police Department. So far, Bertha, which he pulled out of a dumpster five years ago, is the only real dummy working this particular beat. "The only intent is to slow down those people who are violating the law," Atkisson said.

From a distance, the lieutenant said he has seen brake lights quickly pressed and headlights begin to flicker at oncoming motorists. He also has heard truckers heating up the Citizens Band airwaves.

Some callers ask, " 'What is a dummy sitting out in a police car for,' " Atkisson said. He said he responds, " 'It caught your attention, didn't it.' "

"Some call and say it's trickery. They don't like it," he added.

Yesterday, Bertha was stationed all day in a surplus police car on the cobblestone median of Eldon Street in downtown Herndon, which bustles with morning and evening commuter traffic.

Vickie Sullivan, a first grade teacher at Herndon Elementary School, thinks Bertha is a clever idea.

So does Bertha's boss.

Where will she be tomorrow?

"Tomorrow nobody knows but me where she will be," Atkisson said, sounding a bit smug.