A powerful atmospheric river dumped up to 190 millimetres (7.5 inches) of rain near Yuba Gap on 29 October, and a fault in rail-dispatch software helped turn the weather emergency into a six-hour shutdown. Pacific Crest Rail said 61 services were cancelled or curtailed over 36 hours, delaying about 8,600 passengers on the route between Sacramento and Reno.
No train entered an occupied section of track and nobody was hurt. But state officials say 11 trains received conflicting track reservations after the system issued a flood-related closure, then sent an update that did not reach every dispatcher’s screen. The incident has brought fresh scrutiny to software that railway companies increasingly use to coordinate traffic during dangerous weather.
Conflicting instructions on screen
The platform, called SwitchCurrent and made by TrackMosaic Systems, combines rain gauges, water-level sensors and train locations to recommend route changes. Pacific Crest said a sensor near Yuba Gap prompted the closure of a 23-kilometre (14-mile) section. A later update reopened part of the line, but some control-room displays continued to show the earlier restriction.
Dispatchers fell back on radio calls and paper logs, while crews waited for a clear route. Claude Alves, a retired signal engineer who reviewed the sequence for a passenger advocacy group, said the software’s recommendations were useful only if every desk received the same status. “A safe railway cannot run on two versions of the truth,” he said.
A safe railway cannot run on two versions of the truth.
Claude Alves, retired signal engineer
TrackMosaic spokesman Thomas Hofstätter said SwitchCurrent was a decision-support tool, not an automated train-control system, and that human dispatchers retained authority over every movement. He said the company had found a delay in synchronising the closure update, but would not say how long it lasted. Pacific Crest said its crews followed existing safety rules and that no train moved without a confirmed route.
Officials demand manual checks
The state rail safety office ordered Pacific Crest on Saturday to require a dispatcher’s second approval for every software-generated track closure. It also asked TrackMosaic to provide a technical account by 9 November. The operator estimated that refunds and passenger assistance could cost $8.6 million (about €7.4 million), though it has not said how much it will seek from its software supplier.
Passengers criticised the lack of clear information as rain battered stations and flooded roads slowed replacement buses. Craig Sletten, who was waiting in Sacramento with his sister, said announcements kept changing without explaining whether the line was closed for weather or a technical problem. “People can accept a delay. What they can’t plan around is silence,” he said.
Hortense Maggio, who runs a regional passenger group, said the disruption showed why safety decisions should not depend on a single software feed. The group wants Pacific Crest to publish a plain-language account of the system’s role and the locations where alerts failed to synchronise. The railway says it will release a timeline after the state review.
Rail operators have adopted digital dispatch tools to track trains and respond faster to floods, fires and high winds. Alves said automated alerts can help crews spot danger sooner, but only when the system makes uncertainty visible and staff can check it against field reports. Pacific Crest plans to keep SwitchCurrent in use under the new approval rules while the review proceeds.
