Norristown High-Speed Line train operators have been told to slow down in the wake of a crash on the line last month.

SEPTA issued a memo stating the maximum authorized speed on the light-rail line was reduced from 70 miles per hour to 55 m.p.h., officials said. The order was made Sept. 21 and went into effect Monday, according to the memo.

The National Transportation Safety Board (NTSB)  is reviewing an Aug. 22 crash at 69th Street Transportation Center in Upper Darby, where a train on the line ran into an unoccupied train that had been parked at the terminal. The incident caused minor injuries to 42 people on the train. The NTSB issued a preliminary report last week, saying there had been warnings of speed and slippery rails shortly before the crash. The federal agency also reported that the engineer had tried to brake the train, but that it slid through a stop signal. The report stated it had been raining lightly the night of the crash.

Prior to the crash, the operator skidded past the Gulph Mills stop, forcing him to reverse the train to the platform. A passenger on the train who has filed suit against SEPTA in connection with the crash said the train overshot the Bryn Mawr platform as well, though that was not mentioned in the NTSB's preliminary report.

Taking the step of reducing speed limits on the line did not necessarily indicate that speed had been a factor in the crash, said SEPTA spokesman Andrew Busch. He also declined to say whether the change was prompted by information provided by the NTSB.

The NTSB said SEPTA was a participant in the continuing investigation. Eric Weiss, a spokesman for the federal agency, said nothing in the investigation so far has led the NTSB to alert SEPTA to any safety hazards.

"If we have urgent safety information, we can issue an urgent safety recommendation," he said, "but we have not done so in this case."

A source with knowledge of the rail's operations said the speed limits were reduced specifically due to concerns about slippery rail conditions. He added that, in the coming weeks, foliage from trees would exacerbate the problem of slickness on tracks.

After the derailment, SEPTA conducted a review of the brake systems on all the vehicles used on the Norristown High-Speed Line and found no problems.

The NTSB review will likely take the better part of a year, federal officials said.