Extensive resurfacing and renovation work will begin tonight on heavily used Arlington Memorial Bridge, raising prospects of traffic backups until next fall for thousands of rush-hour commuters.

Two lanes of the deteriorating Potomac River span, which is used by about 70,000 cars and buses daily, will be closed throughout the 170-day project. "We expect traffic delays," said Michael Donnelly, regional planning coordinator for the National Park Service, which oversees the federally owned bridge.

The 53-year-old Beaux Arts structure, built to link the Lincoln Memorial with Arlington National Cemetery and to symbolize the union of North and South, has undergone marked decay, mainly within its deck, or paved surface. The work is to include repaving the asphalt surface and replacing underlying concrete.

The $4.7 million project is among a series of recent overhauls of Potomac bridges. Repairs have been completed on the 14th Street, Woodrow Wilson and Chain bridges, and work is under way on the Cabin John crossing. Renovation of Key Bridge is expected to start in late fall or early winter.

The construction work on the six-lane Memorial Bridge, which last underwent major repairs in 1977, is considered likely to cause rush-hour slowdowns and tie-ups on the bridge and on several roads leading to the bridge in the District and Virginia.

On weekday mornings, officials said, drivers heading for the District may face delays in Virginia on the George Washington Memorial Parkway and on a section of Washington Boulevard connecting Shirley Highway with the bridge.

During afternoon rush hours, backups are expected in the District on streets approaching the bridge, including Constitution Avenue NW, E Street NW and 19th Street NW. "Evening rush hour is going to be very bad," said George W. Schoene, city traffic services chief.

Some commuters who previously used Memorial Bridge may switch to other crossings, such as the 14th Street and Theodore Roosevelt spans, officials said. But they warned that these bridges already are congested. Officials urged commuters to consider forming car pools, traveling by bus or subway, or driving to work earlier.

The construction is scheduled to start at 9 p.m., when workers will begin closing off two lanes on the northern side of the bridge.

Throughout the project, officials said, traffic will be restricted to two lanes in each direction. When repairs are completed on each lane, the barriers will be moved to close off other lanes. Traffic will then be shifted to the newly paved lanes.

To speed the work, federal officials offered the contractor, A.A. Beiro Construction Co., a bonus of $4,000 a day for finishing ahead of schedule. The company completed recent work on the 14th Street bridge ahead of schedule, a company spokesman noted.

A spokesman for Rep. Frank R. Wolf (R-Va.) said that Wolf may ask the District to consider funneling more cars onto the 14th Street bridge if Memorial bridge becomes severely backed up. The proposal would entail temporarily lifting car-pool restrictions on the 14th Street bridge during afternoon rush hours, the spokesman said. City officials said the District would be reluctant to ease the requirements, but described the plan as "one possibility.