SCHARON HARDING, ARS TECHNICA
GEAR APR 11, 2024 1:00 PM

San Francisco’s Train System Still Uses Floppy Disks—and Will for Years

Three 5.25-inch floppy disks help keep Muni running every morning. A tech upgrade could take until 2030.

The San Francisco Municipal Transportation Agency, which runs the city's Muni Metro light rail, claims to be the first US agency to adopt floppy disks. But today, the SFMTA is eager to abandon its reliance on 5¼-inch floppy disks—just give it about six years and a few hundred million dollars more.

Members of the SFMTA recently spoke with the ABC7 Bay Area News and detailed the agency's use of three 5¼-inch floppy disks every morning. The floppies have been part of Muni Metro's Automatic Train Control System (ATCS) since its installation in a Market Street subway stop in 1998. The ATCS has multiple components, "including computers onboard the trains that are tied into propulsion and brake systems, central and local servers, and communications infrastructure, like loop cable signal wires," Michael Roccaforte, an SFMTA spokesperson, told Ars Technica.

The floppy disks are for loading the software running the central servers, Roccaforte said:

When a train enters the subway, its onboard computer connects to the train control system to run the train in automatic mode, where the trains drive themselves while the operators supervise. When they exit the subway, they disconnect from the ATCS and return to manual operation on the street.

Roccaforte said initial planning for an overhaul of the ATCS, including moving off floppy disks, started in 2018 and was expected to take a decade from initial planning to completion. Because of an 18-month-long Covid-19-related hiatus, completion is expected in 2029 to 2030. SFMTA expects to settle on a contractor by early 2025 and will release a detailed project timeline then.

{snip}