A firefighter assists a Metro passenger with oxygen aboard a bus after the incident Monday at the L'Enfant Metro Station. (Ricky Carioti/The Washington Post)

Before too many people go overboard saying the Metro transit system is a death trap and all its staff should be fired, as I’ve seen on the Internet, consider the following:

In 39 years of service, the total number of passengers killed while riding on Metro rail cars is 12.

Now compare that to the fatalities in cars, trucks and motorcycles in a single year — 145 deaths in 2013, in the District and the suburban counties that Metro serves.

The comparison isn’t precise, because more people drive than use transit. Still, after adjusting for distance traveled, there’s no question that rail transit overall is considerably safer than, say, the Beltway.

Of course, this is no comfort at all to Carol Glover, who died horribly in a Yellow Line tunnel in Monday's "smoke incident." (What an inadequate term.) Condolences to her family and friends, and sympathy to the 83 who were hospitalized.

Images from the smoke-filled train and rescues at L’Enfant Plaza station in 2015

WASHINGTON, DC - JANUARY 12: Passengers react Monday afternoon as smoke filled a Metro train in a tunnel outside the L’Enfant Plaza Metro station. (Saleh Damiger)

Nevertheless, we need to keep Metro’s latest mishap in perspective.

On one hand, it's right that federal investigators, local politicians and the public take the system to the woodshed again for a highly publicized failure.

On the other, we should resist the rush to ignore transit’s safety advantages. We also should not dismiss the progress that Metro has made on safety since its serious shortcomings were exposed in the 2009 Red Line crash.

A new, peer-reviewed academic study published in the Journal of Public Transportation casts light on the first point. It reports that the rate of passenger fatalities in cars and light trucks is 30 times as high as for travel by subway or light rail. It was based on data in the United States from 2000 to 2009.

“The people of Washington, D.C., are overall much, much safer than if they were living in an automobile-dependent community, like Houston,” said the paper’s author, Todd Litman, who is executive director of the Victoria Transport Policy Institute in British Columbia.

Also, although this is hardly the week to boast about it, Metro took seriously the need to modernize its equipment and instill a safety-minded institutional culture.

The Yellow Line calamity, just outside the L’Enfant Plaza station, just shows it hasn’t finished the job.

This context is necessary because, without it, there’s a risk that a setback like Monday’s will undermine support for Metro to such an extent that the system doesn’t have a chance to recover.

Public transit is already on the defensive. Voters in Arlington rejected the proposed Columbia Pike streetcar. Maryland’s new governor Larry Hogan (R) seems set to scrap the light-rail Purple Line. He would prefer to spend scarce public dollars on roads rather than Metro.

“For those who were already on the fence [about Metro], or the naysayers, unfortunately this [incident] gives them more opportunity to back away from support for Metro at a time when it’s really clear there’s a need for a dedicated funding source and a regional approach,” Jim Dinegar, chief executive of the Greater Washington Board of Trade, said.

We don’t know yet where to assign blame for Monday’s accident. The cause seems to have been some combination of equipment failure (which caused the smoke) and the emergency response (which kept passengers waiting an ungodly long time for rescue).

Nobody can say such an accident was unexpected. Metro had an eerily similar but casualty-free mishap on the Green Line two years ago. It promised to review procedures, conduct new training and drills, and “identify best practice models on train evacuation.”

For the sake of restoring confidence, Mayor Muriel Bowser (D) and others need to insist on providing some basic answers about what happened much more quickly than they seem interested in doing. She seemed tentative and defensive in her comments Tuesday, perhaps because as a former, longtime member of Metro’s board of directors, she shares some responsibility for the failure.

Nonetheless, Metro as a whole, from the directors to the union, have been trying to fix the problems identified in the wake of the Red Line crash.

Metro has been spending $700 million to $800 million a year on rebuilding the aged system, and is more than halfway through the project.

To build a “safety culture,” it was the first system in the country to adopt a “close-call reporting system.” It retrained more than 8,000 employees and contractors in a roadway worker protection program, which was praised as a “best practice” by the American Public Transit Association.

The system’s equipment challenge has been compared to rebuilding an airliner while the plane is in flight. Monday’s events suggest the task requires yet more training for the crew and ground personnel, as well.

It’s worth the trouble.

I discuss local issues Friday at 8:50 a.m. on WAMU (88.5 FM). For previous columns, go to washingtonpost.com/mccartney.