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CTtransit fleet of electric buses remains out of service after summer battery fire

Photo on the left shows an exemplar CTtransit battery electric bus. Photo on the right shows the post-fire damage to the bus involved in the event.
Courtesy of the National Transportation Safety Board
The photo on the left shows an exemplar CTtransit battery-electric bus. The photo on the right shows the post-fire damage to the bus involved in the event.​

The state Department of Transportation says its fleet of 11 electric buses remains out of service after a battery fire in July that triggered a federal investigation.

The National Transportation Safety Board issued a preliminary report about the fire in September detailing how the 40-foot-long electric bus operated by CTtransit became engulfed in flames while parked at a maintenance facility.

The incident sent two maintenance workers to an area hospital where they were treated for smoke inhalation.

“The battery electric buses remain out of service while the investigations are ongoing,” DOT spokesperson Josh Morgan said in an email.

Both the NTSB and the Connecticut State Police are investigating the fire’s origin and its cause.

What we know so far

The NTSB report from September provides some preliminary information about the fire, noting investigations are ongoing and details are subject to change.

On July 23 at about 3:39 a.m., NTSB officials say a 2021 New Flyer Xcelsior battery-electric bus began emitting smoke from the rear compartment while parked inside a maintenance facility in Hamden.

The battery was charged on July 20, but it failed to power up the next day. The bus was placed out of service and stored in a maintenance facility to await inspection by the bus manufacturer.

NTSB officials say a CTtransit worker noticed smoke and heard crackling and hissing coming from the rear of the bus. The worker called the Hamden Fire Department, which responded, but observed no visible flames.

The bus was then pushed to a parking lot to isolate it “from other vehicles and structures.” As a result, two CTtransit maintenance workers were transported to the hospital and treated for smoke inhalation, according to the NTSB report.

Later in the day, at about 7:32 a.m., the Hamden Fire Department responded to the parking lot again. The NTSB report says the bus was once again emitting smoke, “and fire was observed coming from the rear of the vehicle. Fire fighters reportedly had trouble extinguishing the fire and decided to let the bus burn in the controlled environment.”

Battery fires can be notoriously difficult to extinguish. The NTSB report details how the “fire remained active for several hours and fully consumed the vehicle.”

The bus continued to smolder while remaining in the parking lot. The NTSB report says that two days after the fire, “smoke and an orange glow were observed emanating from the right rear wheel well of the burned bus. The Hamden Fire Department responded and extinguished the hot spot.”

What’s next for CTtransit’s battery-electric buses?

CTtransit operated 12 New Flyer battery-electric buses. The DOT’s Morgan says the remaining 11 are out of service while the investigation is ongoing.

The cost of the bus that was destroyed in the fire was approximately $900,000, according to DOT officials.

It’s not immediately clear when the remaining electric buses will be returned to service as NTSB investigations can often take months or longer to complete.

“The NTSB continues to collect information to further examine the events leading up to the fire, the transit company’s safety procedures applicable to its electric bus fleet, and the emergency response to the fire,” the agency says.

Patrick Skahill is a reporter and digital editor at Connecticut Public. Prior to becoming a reporter, he was the founding producer of Connecticut Public Radio's The Colin McEnroe Show, which began in 2009. Patrick's reporting has appeared on NPR's Morning Edition, Here & Now, and All Things Considered. He has also reported for the Marketplace Morning Report. He can be reached at
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