A deadly commuter train crash in Hoboken station in New Jersey renews focus on a mandatory anti-collision system that has been plagued with lengthy, contentious delays.
Officials said train operator NJ Transit has not installed the positive train control (PTC) system in Hoboken or anywhere else on its network.
PTC works by hitting the brakes on a train if the engineer misses a signal to halt—the equivalent of running a red light. How long it takes a train to stop depends on its weight. Freight trains can take up to 2 miles to stop. The system combines GPS, wireless radio, and other technologies, making it far more complex than originally envisioned and requires more investment and time to make it work, according to railroad companies.
By law, NJ Transit is required to have a system in place by the end of 2018. Amtrak has rolled out PTC on its network, while the freight railroads have mostly been rolling out the technology a section of track at a time.
Thursday morning's rush-hour crash killed at least one person and injured 108 others.
National Transportation Safety Board vice chair T. Bella Dinh-Zarr said at a news conference in Washington that the board would "absolutely" look at whether the lack of PTC was a factor.
"PTC has been one of our priorities," she said. "We know that it can prevent accidents."
It is unclear how fast the train in Hoboken was traveling or whether a PTC system would have prevented an accident.
Former NTSB managing director Peter Goelz said that PTC is most effective at higher speeds out on open track, adding it is far from clear it could have made a difference in Hoboken.
Goelz said other factors, such as the alertness of the locomotive engineer, could turn out to be more important.
The NTSB said it would also look for similarities with another crash at the Hoboken station in 2011, when a commuter train struck the bumping post at the end of the track, injuring 30.
Last year, neighboring New York's Metropolitan Transportation Authority received nearly $1 billion in federal loans to implement PTC on its two commuter lines, although it was criticized last month by the federal agency that issued the loan for making almost no progress in installing the system.
NJ Transit ranked second for the most train accident reports nationwide for commuter railroads from January 2007 through June 2016, behind Amtrak.
NJ Transit had 271 accidents, or 18% of the total, compared with Amtrak's 44%, according to data from the U.S. Federal Railroad Administration Office of Safety Analysis.
The rankings in part reflect the heavy use of rail transit in the U.S. Northeast compared with other parts of the United States.
According to a report by NJ Transit to the Federal Railroad Administration for the first half of 2016, the public transport system does not have PTC in operation on its 326-mile network.
Get Data Sheet, Fortune’s technology newsletter.
None of the 1,100 NJ Transit employees who will need training to operate PTC have yet received it, the report said.
White House press secretary Josh Earnest said Thursday "it is too early to tell" whether positive train control would have prevented the crash.
New Jersey Gov. Chris Christie said the train was moving much too fast when it came into the station.
"We don't know what the cause of the high rate of speed was," he said.
PTC was mandated by Congress in September 2008, after a Metrolink train ran a stop signal in Los Angeles and hit a Union Pacific freight train, killing 25 people. Federal investigators faulted the commuter train's engineer, who was sending text messages while on duty.
Last year, the major U.S. freight railroads successfully lobbied for a three-year extension of the December 2015 deadline for implementing PTC, with the option to apply for two one-year extensions. Several railroads have said that they will need both extensions to fully implement PTC.
In June, Lance Fritz, chief executive of No. 1 U.S. railroad Union Pacific, told Reuters the company would have the system fully installed on its 32,000-mile network, but would need the extra two years to "debug" it.
While critics say the railroads are dragging their feet on PTC, the railroads say they have spent more than $6 billion on PTC so far and expect to spend $4 billion more to complete implementation.
John Ireland, a project manager at Arlington, Va.-based railroad consulting firm R.L. Banks & Associates, said cash-strapped public transport operators face a dilemma: They are under pressure to implement PTC while struggling to maintain crumbling infrastructure and handle rising passenger numbers.
"Even the major for-profit freight railroads with their tremendous resources have had a hard time installing PTC," Ireland said. He said putting in the system was "a real scramble" for public transportation agencies because "they operate at a loss and they are not a budget priority for governments in most regions."