The two recent CSX freight train derailments that severed nearby Metro tracks demonstrate the need for tougher federal oversight of railroads and rapid transit systems, a House Energy and Commerce subcommittee chairman said yesterday.

"We're learning that a mixture of freight and passenger trains on a common corridor can be hazardous to the health of passengers and urban neighborhoods," said Rep. Thomas A. Luken (D-Ohio), chairman of the subcommittee on transportation, tourism and hazardous materials. "Moreover, this is part of a nationwide problem of just too many derailments, nearly 4,000 last year."

Luken said the subcommittee was drafting legislation that would require the Federal Railroad Administration to enforce its rules more strictly and to start regulating some areas of rapid transit safety.

S. Mark Lindsey, the FRA's chief counsel, said during a subcommittee hearing yesterday that the FRA is focusing on a broken center beam on a refrigerator car as the possible cause of the partial derailment June 19 of a CSX Corp. freight train alongside the Red Line, north of Metro's Takoma station. A worn track switch is considered the possible cause of the partial derailment Sept. 5 of another CSX train, less than two miles south of the first incident, he said.

"Metro didn't cause the derailments," said Rep. Gerry Sikorski (D-Minn.). The suspected cause "was defective and worn equipment, and that gets into railway inspections," which is the FRA's responsibility, he said.

The FRA has enough inspectors and will evaluate "the adequacy of the CSX inspectors" in an ongoing audit of the railroad's operations in its Baltimore division, which includes the sites of the two recent incidents, Lindsey said.

"I am afraid the Federal Railroad Administration, over the last several years, has lost sight of the importance of preventing accidents," said Rep. James J. Florio (D-N.J.).

Nationally, all types of railroad accident rates have declined in the 1980s, Lindsey said.

The FRA monitors the safety of passenger railroads that use conventional rails, such as Amtrak and the Maryland Commuter Rail Service, but has never monitored rapid transit systems such as Metro. In 1982, Congress stated that FRA has no jurisdiction over transit systems, Lindsey said.

The Urban Mass Transportation Administration, which grants money for transit construction and other projects, uses consultants to watch for safety problems during construction of a system. But once a system is running, UMTA does not inspect the track or monitor operations.

"There's a big void," Luken said. "No public agency, no safety agency, no independent agency has ever inspected or monitored the safety of Washington Metrorail," he said.

Luken said the subcommittee was considering several proposals for tighter regulation, which would:Establish guidelines for building transit systems along parallel railroad tracks. They could include standards for barriers between tracks, separation of tracks, and automatic shutdown of rapid transit trains in the event of interference with the track.

Require the FRA to inspect the track of transit systems.

Slow freight trains in densely populated neighborhoods.

Set strict standards for freight cars carrying hazardous materials.