WASHINGTON — One Amtrak passenger train collided with a CSX freight train while traveling in South Carolina on Feb. 4 resulting in two deaths and over 100 people injured. On Jan. 31, another train carrying passengers to a GOP retreat hit a garbage truck in Crozet, Va. and killed the truck driver. In DuPont, Wash., an Amtrak train was overspeeding when it derailed on Dec. 18, 2017, killing three people and injuring more.

These are the types of accidents that experts say could have been avoided using a safety technology called positive train control. Officials from Amtrak and the Metropolitan Transportation Authority, which runs the New York City’s subway, said they’re working on implementing it as quickly as possible during a Senate hearing Thursday. However, experts are worried that the technology won’t be ready to be in time by a Congressional deadline set for the end of the year.

Positive train control uses roadside sensors and GPS-based location monitoring, among other technology, to track and control trains. The system allows trains to avoid four types of accidents: train-to-train collisions, derailments from overspeeding, collisions into roadway work zones and train movement when a switch is left in the wrong position. In any of these situations, PTC can theoretically slow or stop a train to avoid an accident. Congress has set the deadline for 41 railroads, including 29 commuter railroads, to implement the safety technology by Dec. 31, 2018, with a possibility to extend the deadline by Dec. 31, 2020.

Susan Fleming, director of physical infrastructure for the U.S. Government Accountability Office, painted a bleak picture for current PTC implementation among commuter railroads.

“Our analysis shows that as many as half of the railroads may not meet the deadline or meet the criteria to file for a deadline for an extension,” Fleming said during the Senate hearing.

The GAO’s assessment comes from the fact that there are many challenges posed by implementing this sophisticated and complex technology. Najmedin Meshkati, a professor of engineering at the University of Southern California, explains that installing PTC can be challenging when trains share the same railroad tracks but only some trains have PTC installed. He explains how one shared track in California includes both passenger and freight trains, which might operate under varying degrees of PTC tchnology.

“All of these [trains] need to be equipped with PTC and the track needs to be equipped with PTC and all these train organizations – the dispatch centers with their train engineers  – they need to communicate seamlessly with each other and be able to pass the information and do their job,” Meshkati said, otherwise known as interoperability.

Meshkati also said that there’s a lot of moving parts to physically installing the technology because it includes implementing things like software and hardware, among other components. He said that kind of technology integration can be challenging for railroads to design. Another factor is that field testing the technology while in service is a lengthy process – the GAO says the testing takes at least a year — and must be completed by the deadline.

But there’s been some positive progress to implementing PTC, the GAO says in a recent report. Over half of the commuter railroads reported that they made progress in installing PTC technology on train engines and along the tracks in addition to training their employees to use PTC.

Though PTC is a system that experts believe can avoid train accidents, Meshkati stresses that PTC should be seen as “the very last resort.” Instead, he explained that railroads should be focusing more on their safety culture.

“The safety culture goes beyond simple installation of new technology, specific rules, or rote adherence to standard operating procedures in any organization…[C]reating safety culture means instilling attitudes and practices in individuals and organizations that ensure safety concerns are proactively addressed and treated as high priority,” Meshkati and one of his former doctorate students Yalda Khashe wrote in a commentary on positive train control.