He added that a broken wheel could have caused a catastrophic derailment.
"It's a testament to the equipment that this train did not fall from the track," Dorricott said.
The wheel snapped on SEPTA's R5 line as the train headed to the Thorndale Station, which opened Nov. 22.
The R5 line, from Doylestown in Bucks County to Paoli in Chester County, is one SEPTA's busiest regional rail lines.
The wheel trouble caused rush-hour delays, forcing some rail commuters onto shuttle buses.
The accident also triggered an emergency inspection of eight other Bombardier train cars at the Frazier yard, where the train with the snapped wheel was stored just before the mishap.
No other cracks or fractures were found in the wheels of those cars.
It was only the second time in more than 12 years that a train wheel snapped in two, SEPTA and the railroad union agreed.
Patrick Nowakowski, SEPTA's chief operating officer, said the train was put into service in 1986. A metallurgical test is being conducted to determine what caused the wheel fracture, he said.
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