At 4:40 a.m. on June 19, just north of the Takoma Park Metro station, 21 cars of a CSX Corp. freight train derailed, spilling crosswise over both Metro tracks. Miraculously, no one was injured.

The Metro loudspeaker in L'Enfant Plaza announced the news at 7:20 a.m. as I waited for a connection. In an instant, my mind flashed back 12 years to a meeting of a five-man Metro board of consultants in which we discussed the risks of operating Metro trains in a railroad right-of-way. I had written a scenario that described precisely what had happened -- with one exception. It forecast more Metro fatalities than the world's worst airline disaster. Could such a thing have happened on June 19? Absolutely -- simply by changing 4:40 a.m. to 4:40 p.m.

But why dwell on last month's accident? After all, workmen managed to clean up the damage, haul off the 10 railroad cars that had crashed onto Metro tracks, rebuild the roadbed, and lay new CSX and Metro tracks in less than three days. No one was hurt. Metro riders hardly noticed because it happened over a weekend. So why not just be thankful -- and forget it? Because this accident proved that a massive Metro catastrophe is both possible and probable.

By the time the Metro board of consultants first met in 1974, Metro's design was fixed; certain options to prevent the kind of accident that occurred last month were impossible to implement. The board was forced to elect a warning scheme consisting of a single electric wire on top of a chain-link fence. This system supposedly protects the Metro and CSX trains from each other by sending a signal to the Metro operations center if the hot-wire is broken by an "intruding" train. Then a Metro control console operator notifies the "non-intruder" either by telephone or radio. This takes minutes -- if it is successful.

In fact, the warning system is almost useless. The board had stipulated that the fence be erected between the two tracks at a height of 12 feet above them so that it could warn not only of derailment but also of, say, a shifting load of lumber, steel beams or ammunition on a flatcar that could rip open an entire Metro train without either train leaving the track.

Instead, the board was overruled on grounds that environmentalists would protest the aesthetics of such a fence. The warning hot-wire was thereupon installed on top of a six-foot security fence, which follows the terrain. Since the elevation of the terrain beside the tracks varies widely, there are places in the Metro-CSX corridor where the hot-wire is below track level! Thus, a CSX train could derail onto Metro tracks and never trigger the warning wire.

Cleatus E. Barnett, Metro board member, was quoted saying, "It's a fixed situation at this point. There is no feasible way to change the circumstances at this point."

But there are options:

Install a fence, as recommended, 12 feet above the tracks.

Remove human operators from the warning loop so that when the warning wire is broken, "non-intruders" are automatically and instantaneously warned of intrusion and the 750-volt Metro third rail is deactivated.

Limit the speed of both Metro and CSX trains when passing one another. They now travel at 75 mph and 60 mph respectively.

Schedule CSX trains at periods when Metro trains are either not running or running at infrequent intervals.

Shorten the length of CSX trains. (There were 134 cars in the CSX train in the recent incident. Such length requires both pulling and pushing by locomotives, setting up higher probability of derailment.)

Install direct and mandatory radio contact between Metro and CSX train operators while in the common corridor. (Many trains still do not have cab radios and must depend on track signals.)

Reduce the double jeopardy in the Silver Spring corridor by having only one CSX-Metro interface. (Currently, the two Metro tracks are straddled by two CSX tracks -- producing two derailment boundaries.)

Run Metro and CSX at different grade elevations. (Metro could be elevated above CSX tracks, for example.)

Attorneys for disaster victims often win their cases by arguing that the accident could have been foreseen. This particular Metro catastrophe has been foreseen. What will we do about it? -- Vernon L. Grose is a former member of the National Transportation Safety Board.