The Silver Spring Penguin

A twitchy circuit in Metro’s automated speed controls set up conditions for June’s deadly collision between two Red Line trains, the National Transportation Safety Board reported Tuesday.

Photo: June's Red Line collision killed nine people. Courtesy of Twitter user @jamescampbell.

In an uber-technical, four-page memo to WMATA, the federal agency said 30-year-old track circuits between the Takoma and Fort Totten stations spazzed out during post-accident testing. That action probably sent a false “all clear” signal to one train’s automated controls.

With a virtual green light to proceed, plus a bend in the route that limited sight distance, one train continued southbound, oblivious to the train stopped ahead of it near Fort Totten. The rolling train’s operator did hit the breaks, the NTSB found, but by then it was too late.

The moving train slammed into the stationary one, with the impact tearing open one train car then landing another on top of it. Nine people died and 52 were injured in the collision. Subsequent track work and testing meant for one shitty commute for Silver Springers this summer.

While the NTSB doesn’t tell WMATA to ditch its automated speed-control system, it does recommend that WMATA get its shit together with regular inspections for that specific circuit spasm (technically, a “parasitic oscillation”).

The transit authority said it was already on the case, brainstorming with the control system’s manufacturer on how to detect then quash the problem, a press release said.