MINNEAPOLIS (WCCO) — Every day, roughly 24 different railroad companies send their trains down more than 4,400 miles of Minnesota railway.

For a select few, yearly freight loads reach a level that will require them to meet a new federal safety standards in 2015 called positive train control, or PTC.

Using a complicated network of GPS and ground sensors, the PTC system can override the train’s engineer and slow a train to prevent crashes or derailment in areas like a sharp curve.

“What PTC does is provide an extra layer of protection to make sure the engineer is doing what he or she should do to safely operate the train,” Robert Sumwalt of the National Transportation Safety Board said.

PTC has taken years to develop.  According to railroads, it takes time for companies to integrate the necessary antennas, GPS, ground sensors and signaling systems.

BNSF, Union Pacific, Canadian Pacific and Canadian National are the largest cargo carriers still implementing the technology in Minnesota.

BNSF said in a statement that the company is aggressively installing it in Minnesota: “We have been updating existing signal systems, adding new technology and conducting associated engineering work and will continue to do so.”

BNSF spokeswoman, Amy McBeth, mentioned challenges that have slowed the installation process.

“Antenna installations for the entire rail industry were halted by the FCC for over a year while the agency worked on a permitting process that ensured tribal and historic preservation issues were addressed,” she said. “There is a permitting process now in place that allows us to submit applications for antenna installation, up to a monthly cap.”

Canadian National said it’s committed to installing PTC in Minnesota and will spend $550 million on system-wide PTC installation in 2015.

In a statement, Union Pacific said it invested $385 million in PTC in 2014 and is expected to spend $400 million in 2015.  Union Pacific acknowledged an August 2012 status report that indicated the rail industry wouldn’t be ready by the Dec. 31 deadline due to “significant technical developments, training and deployment, and delays in issuing the final rule.”

There is proposed legislation that would extend the deadline by three years.

Howie Padilla, a spokesman with Metro Transit, said Northstar Commuter rail is in the process of finalizing a contract to add PTC along its routes.

Light-rail doesn’t use PTC, Padilla said. The vehicles have safety devices already in place if an operator can’t control the train.