By Justin Udo

PHILADELPHIA (CBS) — The Federal Railroad Administration tells Amtrak it must make immediate safety improvements on its northeast corridor.

Those safety improvements are updates like the installation of Positive Train Control which automatically slows the train down when it’s going too fast.

CBS News Transportation Consultant Mark Rosenker was the chairman of the NTSB in 2008 when Congress mandated those updates. He says it’s taken longer than anticipated to put them into effect because of a number of factors.

“It’s such a very expensive proposition and there are so many miles, 62-thousand miles, of track in the United States,” he says.

Rosenker says the accident occurred just months before improvements could be implemented.

“That particular area was getting prepared to actually be put on-line, but it needed to have some additional testing done before they could actually activate it,” Rosenker explains.

Rosenker says those improvements have already been made to the southbound side, but not the northbound side where the derailment occurred. Amtrak says they hope to have Positive Train Control completed in the northeast corridor by December of 2015.