NEW YORK (CBSNewYork) — Despite several deadly train accidents over the last several years, MTA Chair and CEO Thomas Prendergast now says Positive Train Control will not be fully installed on the Metro-North and Long Island Rail Road before the end of 2018.

As WCBS 880’s Rich Lamb reported, Congress had set a deadline to have the PTC system, which is designed to override an operator to slow or stop a train when necessary, operating on all railroads by the end of this year.

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“We always had said it was going to be difficult, if not impossible, to meet the end of year deadline,” Prendergast said. “There are discussions in Congress about extending that deadline and we want to put it in the perspective where we’re going to get it in place as soon as possible.”

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Prendergast indicated the first place PTC would likely be installed is on the Metro-North’s New Haven line.

In 2014, an NTSB report concluded that a sleep-deprived engineer nodded off at the controls of a Metro-North train on the Hudson line just before taking a 30 mph curve at 82 mph, causing a derailment that killed four people and injured more than 70 in the Bronx.

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And just last week, an Amtrak train bound for New York derailed in Philadelphia after rounding on a curve going 106 mph in a 50 mph zone. The derailment killed eight people and injured more than 200.