Congress’ upcoming deadline for railroads to implement a complex safety upgrade carries a new gravity after the deadly derailment of an Amtrak train on May 12 that killed eight and injured more than 200 in Philadelphia.

“The accident we have investigated has shown us that we need technology that can step in when humans fail,” Christopher Hart, National Transportation Safety Board chairman, said during a House Transportation and Infrastructure Committee hearing dedicated to last month’s accident.

At issue is a congressional mandate that railroads must upgrade their safety systems by the end of the year, a task most railroads admit they are unable to accomplish. Congress knows this, but is incapable of offering any viable solutions in the near term. Lawmakers are concerned that extending the deadline too far may lead railroads to implement the technology more slowly. But doing nothing would risk putting many railroads in violation of the law, opening rail companies to liability or fines, or being forced to close down service.

Lawmakers have known for years they will likely have to extend the December 2015 deadline for implementing the technology known as Positive Train Control, which provides a failsafe system that can stop speeding trains and enforce important signals that keep trains from colliding.

The time frame has been called “impossible” by the Association of American Railroads, which represents major freight railroads and Amtrak, which will have the technology on only a fraction of its total network by the end of the year.

In the past month, Amtrak has faced significant public scrutiny over its delayed upgrade process.

But Amtrak’s struggle has brought into focus larger issues with the train control mandate that will likely take years to address.

“The question in Congress has not been whether to extend the deadline, but rather how to extend the deadline,” Senate Commerce, Science and Transportation Chairman John Thune, R-S.D., said during a recent hearing on efforts to install the technology on passenger railroads.

The task is massive: Railroads carrying passengers and certain types of hazardous cargo must spend billions of dollars, train thousands of workers and install thousands of pieces of equipment without interrupting service.

The Association of American Railroads has estimated roughly $5.7 billion has already been spent by freight railroads on the technological upgrades, but by the end of 2015 companies will have only equipped 11,000 of the 62,000 miles where the technology is needed.

According to the American Public Transportation Association, publicly funded commuter rail systems have spent $950 million as of April. And a recent survey performed by the group estimated at least $3.48 billion is needed to implement PTC on these railroads nationally.

The Senate has two proposals on the table related to extending the deadline mandated by Congress as part of the Rail Safety Improvement Act of 2008.

Missouri Republican Sen. Roy Blunt’s bill (S 650) has already been marked up by the committee and has two Democrats among the original co-sponsors, Sens. Claire McCaskill of Missouri and Bill Nelson of Florida. The bill would offer a five-year extension for railroads to implement the technology with two additional years after that under certain circumstances.

But Nelson withdrew his support after the Amtrak accident and opted for a measure proposed by Sen. Dianne Feinstein, D-Calif., (S 1006) that would propose one-year, rolling extensions with a full implementation by 2018.

“Congress should be and will be blamed if we postpone the deadline for five or seven years as right now the proposal is to do,” said Sen. Richard Blumenthal, D-Conn. He said senators should back the Feinstein plan.

Issues over ownership of the systems and the railroads are complicating implementation, even on Amtrak’s routes on the Northeast Corridor where the agency has committed to installation by December.

The Federal Communications Commission learned in late May that Amtrak’s Positive Train Control system on the Northeast Corridor and those of freight railroads weren’t designed to be compatible with one another and could have radio spectrum interference that could cause the systems to fail.

Amtrak’s Vice President of Operations D.J. Stadtler told the committee railroad ownership issues are confounding implementation of the technology in other parts of the country. Amtrak may have to close or reroute service in Missouri over a dispute related to who pays for the safety upgrade, he said.

Robert C. Lauby, associate administrator for railroad safety and chief safety officer at the Federal Railroad Administration, said the agency would soon provide Congress with an updated report on railroads’ work to make upgrades against the looming deadline.

But Lauby wouldn’t commit to fining railroads for not meeting the Dec. 31 deadline, despite pressure from Blumenthal at the Senate hearing.

“What we’ve seen here is a failure of will,” Blumenthal said. “Enforcement is about expectations. Right now the expectation is that this law will not be enforced. And right now my fear is that expectation will be self-fulfilling.”

Thune said the FRA’s response is a reflection of the situation. He also said the Government Accountability Office will produce its own assessment of the implementation problem.

“If they levy fines and railroads continue to operate in violation of the deadline and something happens, what’s FRA’s liability?” Thune said after the hearing. “They’re trying to figure out. … How they’re going to handle it on Dec. 31 if there’s no extension. Hopefully before that, Congress will act and we can figure out a good path forward.”