The National Park Service reached a tentative agreement yesterday with Rep. Frank R. Wolf (R-Va.) on a multimillion-dollar plan to ease traffic bottlenecks on a heavily congested section of the scenic George Washington Memorial Parkway between the Theodore Roosevelt Bridge and Spout Run.

The accord, announced by Wolf, provides for parkway improvements at key entrances and exits where rush hour tie-ups occur frequently. Wolf said he had dropped his demand for an additional lane on the parkway, a major issue in a protracted controversy over the federally owned road.

At the same time, Wolf said, the park service plans to support his proposal for an additional inbound lane on the Theodore Roosevelt Bridge, to improve access from the parkway to the District. The added lane on the Potomac River crossing will help siphon traffic from the parkway, Wolf said.

"We have an agreement," Wolf said. "I think this will once and for all solve the problem that we have had on the George Washington Parkway and the TR Bridge." He added that the plan will "help a lot more people to get downtown" without causing environmental damage.

Manus J. (Jack) Fish, the park service's regional director, said last night that he had not made a final decision on the $16.5 million parkway proposal. However, a park service source said Wolf's announcement appears satisfactory to the federal agency and removes the only major obstacle to its plan to improve the highway.

Proposals to widen the Roosevelt Bridge, which is owned by the District, previously have set off objections from D.C. officials, who fear increased congestion on city streets.

"We're concerned about an additional lane because of traffic and we would want to examine closely the implications of an additional lane for traffic movement in the District," Tara Hamilton, a spokeswoman for the D.C. Department of Public Works, said last night.

The tree-lined 1.6-mile stretch of the four-lane parkway, which overlooks the Potomac and a national wildlife area at Theodore Roosevelt Island, has sparked recurrent debate and several studies since the 1950s.

The congestion stems chiefly from the convergence of several arteries, including Spout Run Parkway, with the Key and Roosevelt bridges. The parkway is used by thousands of commuters daily.

Park service officials have objected to constructing additional lanes along that section of the parkway, citing increased costs, possible losses of hundreds of trees and other environmental damage.

According to Wolf, a preliminary draft of a Federal Highway Administration study found that an additional inbound lane on the Roosevelt Bridge would result in "fairly significant improvements" in traffic on the bridge and on a parkway ramp leading to the bridge.

The study, mandated by a congressional measure sponsored by Wolf, found that traffic on the parkway would benefit, although "to a lesser extent." Wolf said the draft report showed that average rush hour speeds on the bridge would increase from the current 15 miles an hour to 33.

Fish said the park service will support Wolf's proposal for another inbound lane on the Roosevelt Bridge. "It would certainly help the parkway," Fish said. Wolf said he will propose a congressional measure to provide the needed $1.3 million to build the lane.

Wolf's plan includes a new parkway ramp leading to the Roosevelt Bridge. Existing ramps would connect Rtes. 50 and I-66 with the bridge. Wolf also said the draft study showed that an improved ramp from the southbound parkway to the inbound 14th Street bridge would reduce traffic hazards.