The San Francisco Municipal Transportation Agency, which operates the Muni Metro light rail system, claims to be the first U.S. agency to adopt floppy disks. But today, the SFMTA is committed to abandoning 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 to the ABC7 Bay Area News and detailed how the agency uses three 5¼-inch floppy disks every morning. The disks have been part of Muni Metro’s Automatic Train Control System (ATCS) since it was installed in a subway station on Market Street in 1998. The ATCS consists of several components, “including computers on board the trains that are integrated into propulsion and braking systems, central and…” local servers, and communications infrastructure such as loop cable signal lines,” Michael Roccaforte, an SFMTA spokesman, told Ars Technica.
The disks are used to load the software that runs the central servers, Roccaforte said:
Roccaforte said initial planning for an overhaul of the ATCS, including eliminating floppy disks, began in 2018 and was expected to take a decade from initial planning to completion. Due to an 18-month break related to Covid-19, completion is expected between 2029 and 2030. SFMTA expects to agree on a contractor by early 2025 and will then release a detailed project schedule.
“Ultimately, our goal is to have a single train control system for the entire rail system,” said Jeffrey Tumlin, SFMTA transportation director ABC7.
Disk error
“If it ain’t broke, don’t fix it,” some say. But while the floppy disk-based train control system currently works, there are challenges to relying on the outdated technology that SFMTA has been highlighting for years.
The transportation agency says the train control system was designed to last only 20 to 25 years, meaning it exceeded its expected lifespan in 2023. In 2020, the Muni Reliability Working Group, reportedly made up of local and national transportation experts, recommended replacing the dispatch control system within five to seven years.
When asked how “bad” it was to update from floppy disks, Tumlin responded ABC7 that it’s all about risk.
“The system is currently working fine, but we know that with each passing year the risk of data degradation on the disks increases and that catastrophic failure will occur at some point,” Tumlin said ABC7.
Previously, the transportation authority claimed that maintaining the ATCS had become more difficult and expensive over time. The challenge of finding workers who know how to use the legacy system was also discussed.
“We need to employ programmers who are experts in ’90s programming languages to continue operating our current system, so we have a technical debt that goes back many decades,” Tumlin told KQED in San Francisco in February 2023.