Cracks in Market-Frankford Subway Cars

A routine inspection in February 2017 revealed cracks in the structure of some of SEPTA’s M4 subway cars used on the Market-Frankford line. The cracks affected the cars’ bolsters, which are the support members that transfer the car’s weight to the trucks below, and allow the trucks to pivot. SEPTA suspects the cracks are related to the area where an air duct for cooling the traction motors was welded to the bolster during manufacturing.