There may be no such thing as a free lunch, but there is such a thing as a free Metro ride in Washington. To get it, you've got to buy a Trailways bus ticket to some out-of-town destination.

The little-publicized Metro refund program began in August and was scheduled to end on Oct. 31. But it was so successful that Trailways has extended it for an indefinite period.

The cash refunds are granted for those who ride either the subway or a Metrobus to the new Trailways terminal at First and L streets NE, off North Capitol Street about six blocks from Union Station (the nearest subway stop, on the Red Line).

To receive the refund, Trailways marketing director Tom Kissell said, ticket buyers have only to produce proof of a Metro ride -- a transfer or a subway Farecard.

William A. Boleyn, Metro's assistant general manager for finance, called the refund "a wonderful idea. If you are traveling, you don't have to worry about getting someone to drop you off at the bus station or pay commercial downtown parking rates."

Now, if only the airlines would do something similar for the airport bus fare to Dulles.