Philadelphia’s public media organization WHYY, also the local PBS and NPR station, reports that the regional public transportation authority SEPTA has sidelined its entire fleet of 25 Proterra electric buses since February 2020.

In an initial report in September 2020, unnamed sources within the agency blamed a defect in the chassis that led to a cracking problem. The absence of the electric buses from service was largely unnoticed by “SEPTA riders during a pandemic era that’s caused record-low ridership.”

In a follow-up report on 15 July, WHYY’s Ryan Briggs wrote that:

Externally, SEPTA has said little about the failed battery bus program or its progress in restoring the buses to service, insisting that it is working on a “resolution” with the bus manufacturer. But internal communications, obtained by WHYY’s PlanPhilly through a right-to-know request, reveal the incident shook SEPTA’s top executives and triggered a serious reevaluation of its plans to convert more of its fleet to electric power. They also show that damage to the buses was discovered even earlier than the agency previously acknowledged—before the buses even began regular service.

In a March 2021 email, SEPTA General Manager Leslie Richards said she planned to tell Federal Transit Administration officials, who helped underwrite the initial purchase of Proterra buses with a $2.6 million federal grant, that she had doubts about “the future of electric vehicle procurement.”

“I plan on explaining why we do not feel the current technology is a good investment at this time,” she wrote.

The report notes that Proterra buses were also taken out of service in Duluth, Minnesota, after officials realized that hilly routes and heaters were draining batteries too quickly. BYD buses were removed from service in Indianapolis for upgrades due to range issues, while officials in Albuquerque, New Mexico, returned 15 BYD buses for similar reasons, Briggs reported.

Proponents, like engineering professor Jeremy J. Michalek, director of Carnegie Mellon University’s Vehicle Electrification Group, said he worries incidents like the mysterious failure of SEPTA’s ballyhooed battery fleet will scare others away from zero-emission vehicles.

“I definitely worry about those kinds of things,” he said. “If we push too fast, too early, and the technology isn’t ready and people have bad experiences, they may be reluctant to try again. There’s only a few ways to move people around without emissions, and electric vehicles are one of them.”

Briggs reports that Proterra told SEPTA that “non-structural skin coat cracks” were first detected in bus chassis in May 2019, but were purely cosmetic, that a repair was on the way purely cosmetic, and that it would not reoccur.

Cracking did recur, in some instances atop prior repairs. SEPTA mechanics also discovered that brackets holding roof-mounted equipment were failing. The buses were taken out of service in February 2020.

SEPTA spokesperson Andrew Busch said because the root cause of the cracking was not identified or corrected by Proterra, SEPTA worried that these cracks could be, or could propagate into, structural issues. A protracted legal back-and-forth began, with Proterra maintaining the buses should be put back into service and SEPTA insisting on a fix.

Proterra maintains that SEPTA’s fleet will be put back into service eventually.