Amtrak experienced a nationwide outage of its federally mandated safety braking system for 90 minutes earlier this month for reasons still being investigated.

The rail operator has until next week to submit a report to the federal government detailing the cause of the outage, but the law does not require those findings to be made public. Amtrak had not immediately responded to an inquiry of whether the report would be made public.

“An unexpected server issue temporarily resulted in delays on Monday (Oct. 3) morning at some stations. Amtrak quickly worked to rectify the situation. This is an infrequent issue, which didn't interfere with other safety mechanisms already in place,” an Amtrak spokesperson said in an email.

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The system that went down is known as positive train control, which is a complex software and radio system that applies the train’s brakes on curves or when it’s supposed to slow down if the locomotive engineer does not. The unfunded mandate from Congress was required to be installed, tested and working by Dec. 31, 2020.

Amtrak is still trying to figure out why back-up servers did not kick in when one failed.

Warren Flatau, a spokesman for the Federal Railroad Administration, said Amtrak is required to file a report about the incident to the FRA within 15 days and then the agency will conduct an in-depth investigation.

“Under FRA regulations, the cause of such a failure must be promptly determined, fully documented, and repaired without undue delay,” Flatau said. “Amtrak will also have to document this failure in its quarterly and Bi-annual PTC performance reports. Part of the reason for such reporting is that the potential for such occurrences was contemplated given the relative complexity of PTC systems.”

Amtrak’s outage raises questions for railroads around the country about how the system works, glitches that surface and how agencies will continue to pay for the expensive maintenance costs.

The disruptions from the 90-minute outage appeared to be minimal, with Amtrak trains already en route unaffected, but that might not be the case next time.

Among the most challenging elements of PTC is that each railroad has its own PTC system, but it must communicate seamlessly with other railroads’ version of PTC because trains frequently run on each others’ tracks. On the Northeast Corridor, for instance, Amtrak owns most of the track, but NJ Transit and freight carriers, like Conrail, also use it.

John Cline, director of government affairs for the Commuter Rail Coalition, said the group's 33 member railroads have not reported a large outage like the one Amtrak experienced. NJ Transit said it has not had any PTC-related outages since the system was conditionally installed in December 2020, agency spokesman Jim Smith said.

Cline said there are ongoing updates and modifications being made, which in large metropolitan areas with multiple railroads is challenging to make sure all the systems are aligned.

"You've got to coordinate it with all the other railroads you interact with, those are the sorts of things that our guys are reporting that are ongoing challenges … and expensive and no end in sight," Cline said.

NJ Transit, the nation's largest statewide railroad, spent $429.6 million to install and test its PTC system and now spends about $5.8 million annually to keep it up to date. For the South Florida Regional Transportation Authority, annual investments to upkeep PTC are between $3.5 million-$5 million, Cline said, adding that it has a much bigger budget impact on a smaller system like that one.

The Federal Transit Administration is currently treating all PTC expenses as being eligible for federal reimbursement, but the coalition is pushing to ensure this is codified into law.

"We certainly would feel better having that very specifically stated in law because you get a different administration in there in the future and they may have a different take on the issue," Cline said. "We envision that ongoing PTC expenses are going to continue to be quite significant and we really think those need to be eligible."