Most of the nation's railroads, including the Long Island Rail Road, will miss a deadline to have train-collision prevention technology installed by the end of this year, federal officials said Friday.

In a 22-page report, the Federal Railroad Administration confirmed what LIRR officials have said for years: Because of several challenges, including a limited number of suppliers, "only a small percentage of railroads" will complete installation of the train-control systems by Dec. 31.

"Positive Train Control is the most significant advancement in rail safety technology in more than a century," U.S. Transportation Secretary Anthony Foxx said in a statement. "We will continue to do everything in our power to help railroads install this technology."

The December deadline was set in the U.S. Safety Improvement Act of 2008, which was drafted after a Los Angeles collision between a commuter train and a freight train killed 25 people.

The technology aims to remove the possibility of human error in several potentially deadly situations. Radio transponders installed on tracks and on trains communicate with each other to automatically slow down or stop a train if it is going too fast, about to hit another train, or violates a signal.

Experts have said PTC could have prevented several fatal accidents, including the May derailment of an Amtrak train in Philadelphia and the December 2013 Metro-North derailment in the Bronx.

Despite spending $11 million last year to shave a year off the project, the LIRR still says PTC won't be largely operational until December 2017, and not fully installed until sometime in 2018.

The Federal Railroad Administration said it has "provided significant assistance" for railroads, including a $1 billion loan to the MTA to fund PTC installation on the LIRR and Metro-North. The agency has also urged Congress to extend the deadline.

If the deadline is not pushed, the agency said it will "pursue enforcement efforts against these railroads," including fines of up to $25,000 a day.

MTA Board member Mitchell Pally said such penalties would not help the project get finished any quicker.

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"The only people who would get hurt are our customers," Pally said. "Every dollar that we have to pay to them is one less dollar that goes into the system."