The rules for transferring between Metro's buses and trains change dramatically when the rail system expands July 1.

Today, the bus-to-train transfer is a simple transaction requiring only that the rider hand his transfer to the station attendant. On July 1, computerized machines will take over the fare-collecting job, and the machines will not accept transfers.

Therefore, Metro riders going from bus to train will have to pay full far on the train after having paid full fare on the bus.

Passengers going from train to bus, however, will be able to transfer. Transfer-issuing machines have been placed in all the Metro rail stations. Rail passengers who plan to use the bus must get their transfers at the station where they board the train. There are no transfer machines at the exit points to the rail stations.

Once riders have completed their train trip, the transfer will be good on any Metrobus. Virginia riders will have to pay bus zone charges, however, while Maryland riders will not. There are no bus zones in D.C. These differences reflect the differing levels of subsidization the three area jurisdictions choose to give the transit system.

Metro has adopted a bus-rail fare structure that will make the cost of a roundtrip requiring the use of both bus and train about the same as the cost of a bus-only trip today.

In the District, however, the basic bus fare rises from 40 cents to 50 cents during rush hours on July 1, so the round-trip cost to rush-hour riders will be more dramatic for D.C. residents.

There are no changes in the bus-to-bus transfer procedures.