SATURDAY NIGHT'S derailment of a CSX freight train near Takoma Park -- an accident that ripped up tracks, damaged a warehouse, forced the evacuation of 200 nearby residents and has disrupted Metro's Red Line service -- shouldn't have come as a surprise. Experts in rail safety have been warning about just such a scenario since the early 1970s, before the Metro tracks were laid parallel to those of the freight line. This summer their predictions came true. Last weekend's derailment was the second in three months, more damaging to property than the first, which occurred in the same vicinity June 19, but because of luck and the lateness of the hour, not as bad as it might have been: if a Metro train had been passing by at the time, scores of people could have been seriously injured or even killed; if it had been rush hour, the number of injuries and deaths could have been in the hundreds -- 1,100 according to one estimate.

The National Transportation Safety Board warned Metro of the risks of building tracks alongside a railroad right of way. But Metro, under pressure to contain costs, rejected recommendations to build either a tunnel or an elevated track between Union Station and Silver Spring. Instead, Metro put up a chain-link fence with an electric wire, which is intended to warn Metro operators of an "intruding" train. But the fence, as the two accidents have demonstrated, can't stop tons of hurtling metal from wreaking costly and potentially lethal damage.

The safety board, which undertook another study of the hazards of this dual corridor after the June 19 derailment, has been discussing several options to prevent future accidents, among them:

Widening the right of way, leaving more space between the CSX tracks and Metro's tracks.

Building a stronger barrier between the CSX and Metro tracks.

Altering the train schedules.

Metro operates between 6 a.m. and midnight. CSX runs its 14 trains throughout the day and night. For optimum safety, neither CSX nor Metro should operate trains during the same time period. Some safety experts and state legislators are already recommending that CSX limit its schedule to the hours between midnight and 6 a.m. This, it seems to us, is the best solution, at least in the short run.

Metro, which failed to heed warnings in the '70s and was slow to act following the June 19 derailment, announced yesterday that it will ask CSX to consider altering its operations. The sooner Metro and CSX -- both of which bear the responsibility for safety -- get together to determine how they can prevent another accident, the better.