On Oct. 12, near Arlington Cemetery, a Metro subway car partially derailed, forcing about 200 passengers to walk about 600 yards through a tunnel to reach the station exit. At that, we got off lightly, for the accident was the train’s third derailment of the day, according to National Transportation Safety Board Chair Jennifer Homendy. Moreover, it stemmed from a problem with the wheel assemblies that the Washington Metropolitan Area Transit Authority has known about for years. Those problems, Homendy said, could have led to a “catastrophic event.”

Metro has since pulled the problematic 7000-series cars from service, leaving the system operating at drastically reduced capacity. Most lines will run one six-car train every 30 minutes. WMATA has said that the service reduction will last at least through this coming Sunday, which actually comes as good news, since it leaves alarmed Washingtonians some hope that the inconvenience will be temporary.

Yet hope mingles with despair, because the gesture toward Sunday is hardly a guarantee, and also hardly the first time we have seen a prolonged service outage due to problems long ignored. Worse still, it has happened during a national ridership crisis for public transit — a fact that may yet turn a minor derailment into a true catastrophe for Washington’s subway system.

Metro’s long-term problems stem from a stew of poor decisions: Initial underinvestment and a complicated governance structure led to chronic underfunding, which resulted in deferred maintenance that was made worse by high labor costs and poor management. Some of those problems have been at least partially resolved in recent years, but the backlog of necessary updates has forced Metro to reduce service, and ridership, so work could be done.

Falling ridership of course means falling revenue, leaving Metro continually scrambling for funding to avoid making even deeper service cuts that would in turn repel even more riders, necessitating further cuts — the dreaded transit death spiral. Further woes emerged with the rise of Uber and Lyft, which appear to have reduced transit ridership in many cities, including Washington. After ridesharing came “micromobility” — electric scooters and e-bikes, which offer a plausible substitute for close-in mass transit, even for the lazy.

Thus, even before the pandemic, Metro seemed to be at risk of a death spiral. The pandemic made those fears not merely real but frighteningly imminent, as basically every major public transit system saw massive ridership declines, particularly on the rail systems favored by affluent workers who had gone remote.

Emergency injections of federal cash staved off the problem for a while. But ridership still hasn’t recovered in most places. In New York City, weekday traffic is down almost 50 percent from pre-pandemic levels, and that’s a relatively happy number; in Boston, weekday trips are down about 60 percent, while in Washington the drop is more like two-thirds, and in San Francisco, a dire 75 percent.

And unlike most earlier woes, the pandemic-induced problems look potentially permanent. Shutting down service for repairs and upgrades may dent ridership for a good long while, but eventually reliable and comfortable service should help win back those riders, and more. Uber and Lyft never seemed to be a long-term threat to mass transit, either, since well before the pandemic played havoc with their business model, those rides were being heavily subsidized by both drivers and investors. It was always clear that eventually, we were going to have to pay a lot more for ridesharing services — at which point, presumably, people would climb back aboard their trains.

Micromobility innovations, on the other hand, might pose a more durable problem. And the pandemic, and the Zoom revolution, clearly pose a more dire one: a possibly permanent shift away from downtown offices.

That’s a disaster in the making for rail systems in particular, since they are far less flexible than buses and are often designed to funnel outlying workers into central business districts. Even a modest shift toward remote or hybrid work could significantly depress ridership, not just because fewer people will be commuting to downtown offices, stores and restaurants on any given day, but because infrequent commuters may decide to move farther out in search of cheaper housing, then drive in rather than ride. Falling ridership means rising costs to carry each remaining worker, and declining voter support for plugging the resulting budget gaps with subsidies. Obviously, the bigger the shift toward remote work, the bigger those problems get.

That makes right now the worst possible time for a major service outage, because so many employers are still deciding when, and how often, to bring employees back. Unreliable transportation is bound to make remote options more attractive to worker and employer alike. If WMATA can get those cars back into service quickly, probably little lasting harm will be done. But if it can’t, one casualty of last week’s accident could end up being Metro itself.