History is close to repeating itself on the Sixth Street off-ramp from the Southeast Freeway, and thousands of commuters must be holding their breaths.

For the second time in little more than a month, the outer lane of the ramp has begun gradually collapsing, with a dangerous tilt to the right. Late last week, the right-hand lane was blocked off with sawhorses, but the left-hand lane has been kept open. In the past few days, a rig from a city contracting firm has been probing the soil to find the source and a solution to the problem.

A month ago, when a similar problem occurred, the entire ramp was blocked off for several days to permit repairs. Traffic headed for the Navy Yard, the Marine Barracks and the east side of Capitol Hill had to take a circuitous and time-consuming detour.

"This time," said Tara Hamilton, public information officer for the D.C. Public Works Department, "we are trying to avoid putting the entire ramp out of service if we can." But there's one problem, Hamilton said: some drivers, notably truckers, are ignoring signs warning them to go slow down the partially blocked ramp. Larger warning signs may be erected temporarily, she said.