After years of confusion and complaints, Virginia and Maryland have agreed to put an end to one of the enduring mysteries of travel on the Capital Beltway: They plan to put up signs identifying it as such.

Transportation workers from both states will soon begin erecting "Capital Beltway" signs and logos at regular intervals along the 66-mile interstate, officials said yesterday. The Beltway currently has a western portion marked I-495 and an eastern portion marked I-95, a situation that has long created problems for motorists unfamiliar with the route.

"The vast majority of people were concerned about being able to give directions," said Marianne Pastor, a spokeswoman for the Virginia Department of Transportation. "If you live at Andrews Air Force Base and you're giving a party and tell someone from Vienna to drive there on the Beltway, he thinks you mean 495. Then he gets across the Wilson Bridge and there aren't any more signs that say 495."

Some perplexing features of the Beltway, the most heavily traveled road in the Washington region, will remain. The dual numerical designations will not change. And there are no plans for the two states to be consistent in how they number their Beltway exits: Maryland identifies them by mileage, while Virginia does it sequentially.

Nonetheless, transportation officials are confident that the new signs will help clear up the confusion. From now on, motorists along the length of the Beltway will be reassured by red, white and blue signs bearing a silhouette of the U.S. Capitol surrounded by a circle.

"We feel that this logo will greatly assist motorists in clearly understanding when they are on the Beltway," Pastor said.

To make absolutely sure, Virginia officials also plan to affix signs reading "Capital Beltway" to existing overhead structures. Maryland officials said they plan a similar effort.

Some details remain to be worked out. Officials said they have not determined when the signs will be installed, how far apart the logos will be or how much the project will cost. A final meeting to resolve those matters is scheduled for Oct. 27, Pastor said.

In the 23-year history of the Capital Beltway, the confusion over its designation is relatively recent. Completed in 1964, the Beltway originally was called I-495 throughout. Interstate 95 connected with the Beltway in Virginia near Springfield, and in Prince George's County near College Park. The plan was to link the two I-95 segments with an I-95 connector through the District.

But then the District decided against the connector and it was decided that I-95 would be routed permanently along the eastern corridor of the Beltway. Under standards imposed by the American Association of State Highway and Transportation Officials, the eastern corridor was renamed I-95 to ensure the continuity of the federal interstate system. The signs for I-495 came down. Officials said they rejected dual signs bearing I-95 and I-495 as too confusing.

"Usually dual-numbered routes create confusion and we try to avoid them," said Neil Pedersen, planning director for the Maryland highway administration. "That's not to say they don't exist." Other officials have said at various times that dual signs would have been too costly.

In any event, highway officials now concede what motorists have been saying for years. Pastor said the Virginia Transportation Department was spurred into action after a Dr. Gridlock column in The Washington Post addressed the problem and advised readers to complain to Pastor and her Maryland counterparts.

Pastor suggested that officials might also consider a uniform system of numbering exits on the Beltway. "This change was brought on by the motorists," she said, referring to the signs. "If there is a similar level of concern on other issues, we'll be happy to look into it."