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Muni runs single-car trains due to continuing shear pin issue

San Francisco transit officials are running single-car trains again Thursday after discovering an issue with the coupler system on its new trains on Wednesday.

San Francisco Municipal Transportation Agency spokesperson Erica Kato said about 10 vehicles are affected and that the transit agency and manufacturer, Siemens, are working fix the issue.

The issue stems from coupler system shear pins that connects the vehicles together. Kato said the pins provided by Siemens only last about three months.

The affected vehicles Thursday have older pins installed, Kato said.

This is not the first time the SFMTA has had issues with the pins — an N-Judah operator in April reported broken shear pins. As a safety precaution, transit officials then decided to run single cars for nearly two months.

Despite the pins breaking during service, safety mechanisms are in place to prevent the vehicles from coming apart, a spokesperson said at the time.

Kato said in a statement the impact will be minimal:

“Most noticeable impact will be today, but this is only about 10 trains that will have less capacity out of the entire Muni Metro system.”

In the meantime, Kato said Siemens is working to develop a more reliable shear pin.

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