A key train safety system is now active on Amtrak rails from Washington to New York.

And SEPTA's Regional Rail system is not far behind in activating its own version of the technology, officials have said.

Amtrak activated Positive Train Control, which can automatically slow or stop a speeding train, between Philadelphia and New York this past weekend.

The system went online from Philadelphia to Washington a week ago, spokeswoman Christina Leeds said Sunday night. The system was already operational on Amtrak rails from New Haven, Conn., to Boston, she said.

Transportation experts have said the PTC braking system would have prevented the fatal Amtrak derailment in Philadelphia earlier this year.

Major passenger and freight lines nationwide were supposed to be equipped with PTC by the end of the year. Virtually all reported they would not be able to comply, and in an October vote Congress agreed to move the deadline to Dec. 31, 2018. Amtrak was one of the few agencies that reported it would have PTC installed by the original deadline; SEPTA was another.

SEPTA won't quite make it by the end of the year, said Jeff Knueppel, the agency's general manager, but it will be close. He expected PTC to be operational on all Regional Rail lines by the end of January, he said in an interview Thursday.

"Things are moving along well, and we're excited," he said.

SEPTA's PTC system requires equipment to be installed both in vehicles and on tracks. The needed equipment is now installed on SEPTA's fleet of Silverliner IV and V train cars, he said.

The new deadline is in part a reason why the system will need another month to bring online, he said. Legislation requires railroads to submit an implementation plan to the Federal Railroad Administration for review, Knueppel said. That plan should be submitted by the end of the year, he said.

The FRA must complete its review and conduct tests on SEPTA's PTC system before it is brought online, Knueppel said.

NJ Transit, another transit agency that must be PTC compliant, has said it would not be able to have the system installed until 2018.

An expansive federal transportation bill passed at the beginning of the month committed $199 million for PTC installation on passenger rails nationwide, but that will cover only a fraction of the cost, which is expected to exceed $12 billion.

215-854-4587@jasmlaughlin