The following editorial appeared in Wednesday's Washington Post: 'The scene is one that no one should ever see ... worse than anything you can imagine.' So reported an obviously shaken John B. Catoe Jr., Metro general manager, after the last bodies of those killed in Monday's horrific train crash were pulled from the wreckage this week. We can't imagine the grief of those who lost family or friends, the pain of those injured or the terror experienced by those who survived the crash. That a routine commute home could turn catastrophic without any obvious cause is, indeed, unimaginable. And that is exactly why it is so critical that officials determine what exactly went wrong as quickly as they can. The National Transportation Safety Board is investigating how and why one train slammed into another on the Red Line, killing nine people and injuring scores more. It was the deadliest accident in Metro's history and the first since 1982 in which riders were killed. Investigators are said to be looking at whether there was a breakdown in the train's electronic safety systems. They will also consider the possibility of error by the train operator who died in the crash. The crash occurred on an open track under clear skies; passengers said the operator -- before the crash -- had announced that the train was holding because another train was in front of it. Why, then, wasn't the driver able to brake in time? Was there a problem with the brakes? Shouldn't the automatic signal system have prevented the impact? Experts say that this kind of accident is theoretically impossible based on Metro's design. That makes the crash all the more unsettling. The age and design of the cars in the train that collided with the stopped train have emerged as possible issues. Apparently, according to Post reporters, brake maintenance was overdue for one train car. The NTSB recommended some safety upgrades that Metro didn't carry out. That failure to act may stem less from recalcitrance than from the juggling of priorities forced upon Metro by its inadequate funding. It's important, in any case, not to jump to conclusions; until the safety board finishes what has been promised to be a painstaking investigation, we probably won't know which of these issues, if any, were factors in the accident. Certain truths did emerge from Monday's tragic events. D.C. and regional emergency personnel did their jobs with competence and compassion. Even more heroic were train passengers who helped to free those who were trapped, fashioned tourniquets and comforted the injured. Most telling was the reminder of Metro's importance to the Washington region. The crash's impact extended far past the Takoma and Fort Totten stations to the tens of thousands of people who depend on Metro to get them to jobs, homes and play. And it is for that reason, as well as to keep faith with the victims, that Metro must ensure that -- whatever the cause -- such an accident never happens again. 