The Whitehurst Freeway was turned into a one-way roadway yesterday, catching hundreds of drivers by surprise on the first day of construction and causing scattered traffic problems in Georgetown and Foggy Bottom.

Despite being warned by District officials for several weeks that the freeway would be reduced from four lanes to two lanes in one direction, many drivers continued using their same route yesterday and paid the price with long waits, especially along M Street NW in both directions and inbound on Canal Road. About 50,000 vehicles each day use the elevated freeway along the Georgetown waterfront.

"Clearly, the message isn't out yet, or people don't believe it," said Tara Hamilton, spokeswoman for the D.C. Department of Public Works.

While the bridge deck, or roadway, is being replaced during the next 15 months, the Whitehurst will be a one-way operation and the two ramps connecting the freeway and Key Bridge will be closed. The only time motorists will be allowed to drive in the west, or outbound, direction is from 2:30 to 9 p.m. weekdays. At other times, the two lanes will be open in the east, or inbound, direction.

The irony was that the Whitehurst itself flowed relatively smoothly most of the day, as did traffic on Key Bridge connecting Rosslyn and Georgetown. The trouble spots were at both ends of the freeway, where drivers enter and exit, especially Canal Road and the Rock Creek and Potomac Parkway near the Kennedy Center.

Drivers showed their lack of knowledge about the change at the ramp carrying traffic from Key Bridge to the eastbound Whitehurst. Despite signs and other information that warned motorists to avoid the ramp as of yesterday morning, commuters streamed onto the ramp as if they were unaware of the construction project. The ramp was permanently closed last night.

A reporter counted 286 vehicles on the ramp from 7:45 to 8:15 a.m.

Drivers couldn't be blamed for some of the traffic problems, however. The city and contractor opened the outbound lanes 15 minutes late yesterday afternoon, causing dozens of cars to head onto lower K Street and up to Wisconsin Avenue NW, which contributed to congestion on westbound M Street that rivaled traffic on a Saturday night.

The morning rush hour's worst problem occurred when commuters, many from Maryland heading west on Independence Avenue NW, ignored a detour and tried to take the Rock Creek and Potomac Parkway to the Whitehurst Freeway to travel outbound to Canal Road and other points. Finding the Whitehurst closed, many drivers spilled onto M Street NW through Georgetown.

D.C. traffic officials prefer that these drivers take the Theodore Roosevelt Bridge into Rosslyn, turn onto Key Bridge and come across the river to make the turn onto Canal Road.

During the evening, problems developed when many Virginia-bound vehicles exiting the Whitehurst Freeway at Canal Road turned right to get back to Key Bridge because the ramp to the bridge has been closed. As a result, inbound traffic on Canal Road was backed up more than a mile.

"This is not normal," Elijah Wiggins, a mechanic at an Exxon station at 36th Street and Canal Road, said about 3 p.m. "It moves pretty well this time of the day."

Hamilton said signs will be up by tomorrow prohibiting drivers from making a right turn when they come off the Whitehurst.