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SF’s Market Street subway runs on Reagan-era floppy disks

A MUNI bus passes by the Powell Street BART station on Tuesday, January 21, 2020. | Carlos Avila Gonzalez/The San Francisco Chronicle via Getty Images

San Francisco already knew that its transit agency resorted to plastic beer-pong cups to stop leaks in the Central Subway tunnel before it officially opened for service. Now it turns out the SF Municipal Transportation Agency is using woefully outdated technology for crucial operations: 5-inch floppy disks.

“Our train control system in the Market Street subway is loaded off of five-and-a-quarter inch floppy drives,” SFMTA director Jeffrey Tumlin told KQED’s Priya David Clemens this week.

In other words, some of the frustration we experience when the N-Judah wreaks havoc on our commutes can be pinned on technology that was popularized by IBM during the Reagan Administration. 

Perhaps more ominously—or as a subtle call for a federal cash boost—Tumlin compared the situation to Southwest Airlines’ recent meltdown.

Reached for comment, SFMTA spokesperson Stephen Chun acknowledged that the Automatic Train Control System relied on aging equipment.

“We recognize that any failure of the outdated equipment is certain to impact everyone working on or riding Muni,” Chun told The Standard. “Fortunately, our crew makes the difference between these failures crippling the system for weeks or for just a few hours.”

The use of floppies is hardly some previously unknown fact; for starters, Tumlin explicitly told KQED that his agency has to retain staff with skills honed to what amounts to the programming equivalent of Ancient Babylonian.

But Twitter users on Thursday expressed surprise that a city known as a global tech capital would be so reliant on a storage format that lacks the capacity to store a single hi-resolution photograph.

SFMTA is hardly unique in using them, however. As recently as 2020, British Airways was loading avionics software onto 747s via floppy disk.

Five-inch floppy disks are still used as the save icon on computers worldwide, although they've long since become obsolete. | Getty Images

Technology certainly has improved since the ’80s: An iPhone has 100,000 times the computing power of the machines NASA used to put men on the moon, to say nothing of the disks that many people over 40 remember sliding into the “A” drive of their Gateway 2000.

For those who’ve never had to use one—and keep it far away from any magnets—floppy disks are still used as the “save” icon on computers worldwide, but they’ve been obsolete for 30 years or more. Originally a full eight inches across when introduced in the 1970s, floppies later shrunk to five-and-one-quarter inches, and, eventually, a mere three. Early generations were indeed bendable, although the final generation was made of a harder, thicker plastic, with no flop at all. Eventually, CD-ROM technology superseded them before becoming nearly extinct, too.

This story has been updated to include comment from SFMTA.

Astrid Kane can be reached at