A crucial piece of safety technology that helps prevent trains from travelling too fast was not installed on the service that crashed in Hoboken on Thursday morning.

Passengers aboard the No. 1614 Pascack Valley line train say it never slowed down before slamming through barriers and into a wall at the New Jersey station.

A witness at the scene said the engineer was found slumped over at the wheel of the train.

Now it has emerged that the train lacked a system called Positive Train Control (PTC), which combines satellite and computer data to monitor train movements and prevent them from going too fast or hitting other locomotives on the track.

A mandatory report by Federal Railroad Administration revealed that the life-saving technology is not installed on any NJ Transit locomotives.

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A woman is seen lying on the ground next to the crashed train as NJ Transit workers survey the damage

Passengers run to safety through debris after the NJ Transit train crashed in to the platform at the Hoboken Terminal

The PTC can override an engineer's actions - or lack thereof if, for any reason, they are unable to take control of the train.

Computer algorithms calculate the distance between a red light and a train. If a train is moving too fast for an engineer to stop safely, the backup safety system intervenes and automatically applies the brakes.

'It will not allow you to violate a speed restriction, a work-zone restriction or a red signal,' Joseph Szabo, a former head of the Federal Railroad Administration, told AFP. 'It just won't let you violate it.'

The system helps allow for human error or if an engineer is suddenly overcome with illness.

The National Transportation Safety Board has been calling for the national implementation of positive train controls for decades.

The board has said that over that time it has investigated at least 145 PTC-preventable accidents in which about 300 people were killed and 6,700 injured.

An injured woman is evacuated from the New Jersey train station after the deadly crash. Witnesses said some passengers were trapped under concrete on the platform

A passenger who was travelling on the crashed train is seen on the floor of a parking lot with a neck brace

'While the NTSB has called for a system like this for over 45 years, it still has not been fully implemented in our commuter, intercity, and freight trains. Without it, everybody on a train is one human error away from an accident,' the agency said.

An investigation into a 2008 crash between a Metrolink passenger train and a freight train in Chatsworth, north of Los Angeles, which killed 25 people and injured 135 others, found the collision could have been avoided if PTC had been installed.

Following the tragedy, politicians passed a law requiring the nation's main rail firms to implement a safety system by the end of 2015.

But progress has been painfully slow and last year, Congress passed a bill that grants a three-year extension to railroads before they have to install the long-sought safety technology.

Railroads have already had seven years to install PTC, but most weren't expected to meet the end-of-year deadline to put it into operation on all tracks that carry passenger trains or are used to haul liquids that turn into toxic gas if spilled.

As a result, railroads and companies that ship freight by rail have been strongly urging Congress to provide a delay.

Freight railroads, worried about fines and liability should they violate the deadline, threatened to stop hauling cargo like chlorine, which becomes a toxic gas when exposed to the air, and prevent commuter trains and Amtrak from using their tracks if the deadline was not delayed.

The bill granted railroads until December 31, 2018, to install the expensive technology, and they can seek a waiver for up to another two years if needed.

Railroads remain 'fully committed to being fully accountable and transparent in completing PTC,' said Ed Hamberger, president of the American Railroad Association.

But Sen. Barbara Boxer, D-Calif., attributed passage of the bill to lobbying by railroads, among the most powerful interest groups in Washington.

'People are dying, they're being injured because we don't have positive train control,' she said. Congress is likely to be faced with more requests for delays in the future 'if we're not really looking over the shoulder of the railroads,' she said.

The bill also extended the government's authority to spend money on transportation programs.

Rollout of PTC has varied widely across America's vast railway network and the dozens of freight and passenger companies that use it.

But PCT was not installed on the Amtrak Northeast Regional train, travelling from Washington, D.C. bound for New York City on May 12 last year, which crashed killing eight and injuring more than 200.

Positive train control 'would have prevented the accident, had it been monitoring the trains that collided,' the NTSB said in a document called 'Most Wanted Transportation Safety Improvements' for 2015.

Former Amtrak CEO Joseph Boardman said last year, shortly after that crash, that Amtrak began installing positive train control in the 1990s.

'We had to change a lot of things on the corridor to make it work, and we're very close,' Boardman said. 'We have delivered a leadership role in positive train control in the United States.'

The crash led to renewed calls for backup safety systems but the system was not installed on the Pascack Valley line train when it crashed today.