SEPTA on Wednesday debuted the first of its new ACS-64 locomotives, which are key to modernization of the the agency's aging Regional Rail fleet.

Locomotive 901 made its ceremonial inaugural run from SEPTA's Chestnut Hill East station in advance of getting to work on the Paoli-Thorndale Line, Regional Rail's busiest.

SEPTA has ordered 15 of the Siemens-built electric locomotives at a cost of $154 million.

SEPTA general manager Jeffrey D. Knueppel said the agency had received eight of the engines. Four more are en route from the factory in Sacramento, Calif., and the remaining three are due in August.

He said SEPTA hoped to have all of them in operation by October. Amtrak already operates ACS-64 locomotives on the Northeast Corridor.

The ACS-64s are replacing SEPTA's aging fleets of AEM-7 and ALP-44 locomotives, and are equipped with positive train control, an advanced system designed to automatically stop a train from running into another train or speeding,

Kneuppel noted that SEPTA's old engines are the last of their kind in commuter rail operation in the United States.

He joked that he was considering cutting up the old engines and turning them into paperweights to give to riders who complained about service in the past.

Starting in 2020 and 2021, the locomotives will pull double-decker coaches that are capable of carrying more passengers than standard coaches. SEPTA plans to buy up to 55 of the coaches at cost of $174.3 million.