(Bloomberg) — The third fatal Amtrak crash in less than twomonths has thrown a spotlight on delays in installingcongressionally mandated technology designed to automatically slowtrains and prevent collisions.

New system work

In the most recent episode, work to install the new system,known as Positive Train Control, might itself have contributed tothe crash outside Columbia, South Carolina, on Sunday, federalofficials said. Employees had temporarily lowered the safetyprotections on the set of tracks where an Amtrak train en routefrom New York to Miami rammed into a parked CSX Corp. freighttrain.

Two Amtrak employees died and more than 100 people werehurt.

The collision would not have occurred if a PTC system had beenfunctioning there, said Robert Sumwalt, chairman of the U.S.National Transportation Safety Board. The NTSB said the samething after an Amtrak train derailed near DuPont, Washington, onDec. 18 when an engineer failed to slow down for a curve,killing three people. PTC would have sensed where the train was andautomatically slowed before it reached the curve.

'People are dying'

"People are dying," U.S. Representative Sean Maloney, a New YorkDemocrat, said in a statement. "We can't wait any longer on gettingPTC systems up and running nationwide. Congress has delayed thisdeadline time and again and we've seen the deadly results."

Despite the NTSB's decades-long recommendations for PTC, andCongress in 2008 mandating it by 2015 on critical sections oftrack, many railroads are still years away from completion. In late2015, when it became clear that railroads wouldn't meet thedeadline, lawmakers extended it until this year. If railroadsinstall PTC equipment across their systems and get it operationalon at least half of their lines, they can take another two years tocomplete the task.

The other fatal Amtrak crash occurred last Wednesday in Virginiawhen a train carrying Republican lawmakers struck a trash truckdriving through a grade crossing. An occupant of the truck died.The PTC systems mandated by Congress can't detect vehicles at agrade crossing, so it wouldn't have prevented that accident.However, some similar systems do monitor grade crossings, likealong a section of Amtrak rail in Michigan.

NTSB meeting today

PTC was also raised as an issue Tuesday at an NTSB meeting toconclude investigations into two New York-area transit systemaccidents. Within 13 weeks in late 2016 and last year, trainsoperated by New Jersey Transit and Long Island Rail Road slammedinto posts at the end of rail lines after engineers failed to stop.The crashes killed one and injured more than 200.

Because of PTC's limitations, neither transit system could usethe safety system within the stations, so it would have been unableto prevent either accident if it had been installed. The NTSBissued a recommendation calling on U.S. regulators to developanother automatic system that works in stations.

U.S. FederalRailroad Administration (FRA) data shows thatrailroads carrying people have on average lagged far behind freightsystems in installing PTC.

Amtrak is an exception and has almost completed itsinstallation, according to FRA data. However, most U.S. railtransit systems are lagging, according to FRA. New Jersey Transit,for example, had completed installing just seven percent ofrequired PTC hardware through the end of September.

Overall, passenger lines are operating PTC on 24% of their routemiles, compared to 45% for freight systems.

Technical hurdles

Railroads have encountered many technical hurdles that madeimplementing PTC more complex than first thought, according to theAssociation of AmericanRailroads, an industry trade group. Companies must equiplocomotives with PTC technology, install thousands of waysidesignals and communications towers as well as build up the networkof computer servers to make the system work, each with its own setof challenges.

CSX, which owns the track where Sunday's crash occurred,declined to comment on the NTSB account, other than to say that itwas cooperating with the investigation.

Related: NTSB says speed control system could have preventedWashington state Amtrak crash

The Amtrak train was diverted from the main railroad track to aside area where the CSX freight train had been parked. The switchconnecting the main line to the side area hadn't been returned toits normal position after the freight train entered the area,according to the NTSB.

Before the NTSB briefing on Monday, Bryan Tucker, a spokesmanfor CSX, said that the railroad was on schedule to meet the 2018deadline for installation of PTC and to have the system fullyoperational by 2020.

Workers disabled hazard signals

As the railroad performed maintenance to install PTC in theSouth Carolina stretch of track, workers disabled signals thatnormally warn train engineers of hazardous conditions.

Such operations are permitted so long as an engineer getspermission to operate from a railroad dispatcher, Sumwalt said.

Related: Engineer's speed prior to deadly Amtrak crashremains puzzle

He declined to say what CSX workers have told investigatorsabout what allowed the switch to remain in the wrong position andwhat the Amtrak train's dispatcher, who was also a CSX employee,was told about the status of the track.

Freight railroads have completed installation of PTC on 56% ofrequired rail sections, according to the AAR. Commuter rail systemsare not included in the totals. Amtrak has finished the work ontrack it owns between Boston and Washington.

Implementing the system has taken railroads longer thanexpected, according to Tom Schnautz, an assistant vice president ofNorfolk Southern Corp. He said his railroad had planned to installtrack-side monitoring systems and radio antennas concurrently buthad to halt antenna installations for a year because of lengthyregulatory reviews it had not anticipated at the outset.

"We continued with the installations of wayside locations andleft the antennas laying on the ground and had to come back later,"said Schnautz, who co-chairs a PTC committee at the AAR. "That wasa very significant issue at that point."

The cost of the system is expected to exceed $13 billion justthrough this year, according to the AAR.

Have railroads ignored business benefits of technology?

Railroads have at times been their own worst enemy developingPTC, said Steven Ditmeyer, a former official at theFRA who teaches rail management at the University ofDelaware.

PTC uses global-positioning satellite technology and tracksensors to monitor every train's location and can automaticallyslow or stop a train if there's a speed restriction or obstructionahead. It can also be a huge efficiency boon, allowing trains tooperate closer together and speeding arrivals, according toDitmeyer and a 2004 Federal Railroad Administration study.

Railroads could save from $937 million to $2.1 billion a yearwith PTC, the study found.

Related: Amtrak engineer said to be distracted before deadly2015 crash

"Most of the railroads have ignored the business benefits thatcan derive from this technology," Ditmeyer said. That has, in turn,created incentives that have slowed its introduction, he said.

"It's implementation and its integration has been far moredifficult than they imagined," said Peter Goelz, the formermanaging director at NTSB who is now a lobbyist at O'Neill &Associates in Washington. "But that's not to say that some of therailroads weren't dragging their feet at the onset."

Whether the latest accidents will push PTC into operation sooneris an open question.

Growing pressure to install PTC

Augustine Ubaldi, an engineer at Robson Forensic Inc. in Ohiowho has worked on large railroad infrastructure projects, predictedthere will be growing pressure by lawmakers to install the system.But it would be a mistake to move simply for political reasons,Ubaldi added.

The complexities that have delayed its installation arelegitimate and railroads should be allowed to use simplertechnology, he said. In addition, Positive Train Control won'tprevent some railroad accidents, like derailments because ofdefective tracks.

"I don't want people to think it's a magic bullet and we won'tever have enough another train derailment as soon as PTC goes intoservice," Ubaldi said.

Related: 9 injured after commuter train derails inCalifornia