What is Positive Train Control, and would it have prevented the Amtrak wreck?

The president of Amtrak, Richard Anderson, said Monday that the PTC system was not in use on the stretch of track where the train derailed.

What is PTC and could it have prevented Monday’s crash? Here’s how it works. 

A head-on crash between a freight and passenger train near Los Angeles in 2008 that left 25 dead spurred Congress to enact the Rail Safety Improvement Act. The act required all major U.S. rail lines to implement the PTC system. That process – installing the system on trains and rail lines – was to be completed by the end of 2015.

What Congress did not address at the time was the cost for the system. The Association of American Railroads estimated the cost of the PTC system at $22.5 billion over 20 years – making the requirement the costliest regulatory expenditure ever imposed on rail systems.

Congress was persuaded to extend the deadline by three years for most companies (some by five years if certain measures were met), giving rail companies until Dec. 31, 2018, to have the systems in place.

PTC has been fully implemented on only 456 miles of rail tracks.

What is positive train control and how does it work?

The system, using GPS to monitor a train's location as it moves along its route, is designed to slow down or stop a train to avoid a collision with another train or a derailment if the train is going too fast for the area or conditions.

The system uses a connection between a train's onboard computer, 'ping' points along a rail route and dispatch stations. Before leaving on its trip, the train’s computer system downloads information about speed limits, construction areas or any other possible hazards along its route.

As the train travels along its route, the “ping” points along the rails keep the train’s computer in contact with a dispatcher. The system transmits information about the train such as its speed and any problems or conditions that would require the train to slow down.

If there is a problem, the train’s conductor is alerted. If for some reason the conductor does not or cannot respond, the train can be slowed or stopped by the system via the onboard computer.

Why wasn’t it in use to prevent Monday’s Amtrak derailment?

Sound Transit spokesman Geoff Patrick told CNN that while PTC was in place on segments of the track that the Amtrak train was using, the system was not fully implemented. Sound Transit, which owns the track where the train derailed, said the target date for full implementation of its PTC system – tracks and trains -- is the second quarter of 2018.

How many trains and how much track does has Amtrak have equipped with PTC?

As of the second quarter of 2017, Amtrak has equipped 49 percent of its locomotives and 67 percent of its tracks equipped with PTC. The PTC safety plan submitted to the Federal Railroad Administration for approval has been conditionally certified.

As of March 2017, freight railroads had spent $8 billion on PTC systems and passenger lines had spent $3.5 billion on the system.

Here, from the AAR, is a list of the complexities involved with implementing the PTC system:

Developing PTC Technology: Much of the technology PTC requires did not exist when the mandate became law in 2008. Railroads had to develop the required technology for locomotives, wayside interface units and back office systems from scratch.

Deploying hundreds of thousands of technology pieces: PTC involves the deployment of hundreds of thousands of technology pieces — from onboard locomotive systems to switch position monitor — across the nationwide rail network.

Geo-mapping 60,000 miles: The approximately 60,000 miles of railroad right-of-way on which PTC technology will be installed and 486,000 field assets (i.e. mileposts, curves, grade crossings, switches, signals, etc.) must be precisely geo-mapped for PTC technology to work correctly. This mapping forms the basis for the system's track database used by the back office server.

Interoperability is essential: To function properly, PTC systems must be interoperable so that any train operating on another railroad's network can communicate with the host railroad's PTC system.

Equipping 1,900 "dark territory" switches with power: Some long stretches of track in remote areas use only one main line without any signalization. To make these areas PTC compatible, railroad switches must be upgraded and electrical power must be brought to the site.

Phased rollout is critical for safety: Implementation of PTC must occur in phases and location by location, starting with less complex areas and proceeding to the more operationally complex areas with lessons learned incorporated at each step to ensure that the system functions safely.

Required testing software is not available: Once all testing of individual PTC components is complete and those components have been installed, testing of the entire system as a whole can begin.

Training cannot be completed until the PTC system is operational: PTC requires rigorous training for 125,000 Class I railroad and commuter rail employees, which will be completed in parallel with installation and deployment. Training will happen before the system is turned on.