As the future of Union Station is being hashed out in Congress, the American Bus Association and two major bus companies - Greyhound and Trailways - are hoping that a long standing proposal to add a major bus terminal will not be forgotten.

A Union Station location would be a brass ring for the bus companies who hope to become part of a major ground transportation system that will help them compete with Amtrak.

The inclusion of a bus terminal at Union Station was first proposed by the Department of Transportation in 1974 as part of a plan to upgrade the station. Congress never acted on the plan, however, because of the cost, estimated to be $50 million for just the bus station.

Although the bus companies' current proposal is much less expensive, around $10 million, there so far appears to be no takers in the Congress. Neither the House nor Senate subcomittees' proposals for the future of Union Station includes a bus terminal.

Union Station has been the target of criticism for its cost overruns in the construction of a 4,000-space parking garage and the development of the National Visitor Center.

Ted Knappen, senior vice president of Trailways, said that Trailways would be willing to close its downtown station - despite the fact that the company has recently spent $750,000 for renovations there - to become part of a Union Station transportation center.

"It's of absolute necessity," he added.

A spokesman from Greyhound said her company has just spent more than $1 million to renovate its downtown terminal, but quickly added: "We want to be a part of anything that should materialize at Union Station."

The reason the bus companies have their engines roaring over the possibility of becoming part of a ground transportation center at Union Station, according to Knappen, is because they are "in heads-up competition with Amtrak6.

"The figures themselves prove the point," said Knappen, who added that Trailways has maintained its passenger level throughout the country, but has taken dramatic losses in the North-east corridor.

"If things continue, Amtrak will be using Uncle Sam's money to put us out of business," added Knappen. As it stands, he said, the Union Station project will only benefit the rail transportation system at a cost of nearly $100 million.

Knappen said that a recent governmental study of the Northeast corridor showed that an improved rail system would lure an estimated 28.6 percent of the current bus ridership to the rail system.

In light of the current controversy over Union Station, government officials are reluctant to spend the additional $10 million needed to acquire land and build the bus terminal, transportation officials say.

Under the current bus company proposals, the government would acquire the land and building adjacent to Union Station that is now owned by B & O Railroad. The government would then raze the building, construct the terminal and lease it to the bus companies.

The current House subcommittee proposal calls only for the completion of the visitor center at Union Station, while the Senate version calls for only the development of the rail portion of the station.