Federal rail safety specialists recommended yesterday that Metro and CSX Corp. make several equipment and operational changes along their parallel railroad tracks to minimize the danger of another freight train derailment like the two that disrupted Metro Red Line service during the summer.

Members of the National Transportation Safety Board, complaining that they needed more information to support the recommendations, asked the staff to conduct further study before they acted on the four proposals.

The safety board began an investigation after the June 19 CSX train derailment that severed nearby Metro track north of the Takoma station. A subsequent CSX train derailment Sept. 5, which cut Metro's track near the Fort Totten station, was included in the study.

No passenger train was operating near the crash sites at the time of the derailments and the accidents caused no injuries.

But the specter of a rush-hour Metro train running into a derailed freight train spurred the safety board staff to recommend four interim measures to reduce risk at least until the completion of the investigation sometime next year. The staff proposed that:

CSX not operate freight trains during Metro's morning or evening rush periods in the shared corridor between Washington's Union Station and Silver Spring. At rush hour, Metro's Red Line trains run every three minutes and can be packed with up to 800 riders.

CSX remove "pusher" locomotives from trains operating in the corridor. Railroads place the 200-ton locomotives at the rear of long trains to power them over hills. The pushers, which are needed to traverse the mountainous terrain of Western Maryland, are not needed east of Gaithersburg, according to the safety board staff. Along the downhill incline from Silver Spring to Union Station, a pusher locomotive can cause freight cars to bunch closely together, increasing the chance that a minor problem can cause cars to slip the rails, the staff said.

A CSX spokesman said the company will consider both proposals, if they are adopted by the safety board.

Metro alter the warning fence between the parallel tracks to automatically stop a Metro train when the fence is tilted or knocked down. The warning system now alerts Metro officials, leaving them with the responsibility for halting trains.

The safety board noted that Metro already plans to change the system so that it electronically stops trains in the vicinity without cutting power to the rails, so that an operator can immediately guide a train out of the area of the accident.

Metro raise the height of its warning fence so that the top is at least 12 feet above the CSX track bed. Metro is studying the issue of the fence height, said safety director Roger Wood.