With little public notice, the D.C. Department of Transportation reduced rush-hour commuter traffic on busy 16th Street from three lanes to two lanes yesterday and, according to some who use that way to work, produced one of the worst traffic jams in memory.

Alice Edwards, who works in downtown Washington, put it this way: "I started to go from Silver Spring down 16th Street and at Blair Circle," which is at the District-Maryland line, "we found to our horror we weren't going anywhere . . . In my rear-vision mirror, I swear I could see people crying."

Tara Hamilton, the D.C. DOT spokesman, said the department eliminated the center reversible lane of the five-lane street, making the traffic flow two lanes in each direction at all times instead of three-and-two in the rush hour, favoring inbound in the morning and outbound in the afternoon. The middle lane is now for left turns only.

The reason for the change, Hamilton said, is that two months from now the department will begin rebuilding 16th Street between Arkansas Avenue and Emerson Street, requiring the shutdown of one lane in rush hours and additional lanes at other times. "We wanted to give motorists the opportunity to adjust their travel patterns," she said.

But Hamilton said she learned of the timing of the change on Friday, too late to issue more than a perfunctory last-minute announcement to news media. She said signs were posted Friday along 16th Street announcing yesterday's restriction, triggering several "calls Friday morning asking, 'What crazy thing are you doing?' "

She urged motorists to switch to Metro or to drive via Georgia Avenue.