August 2010

Positive Train Control Implementation Signals Challenges Ahead

by Janna Starcic, Executive Editor

Despite having reached a milestone by submitting their positive train control (PTC) implementation plans to the FRA by the April 16, 2010 deadline, the rail community still has a long road ahead in terms of what they have to accomplish.  But, the end of that road, a Dec. 31, 2015 deadline for installation, is approaching rapidly.

This story will focus on the technology as well as the challenges rail systems face, such as costs and interoperability.

Breaking it down

According to the FRA, the Rail Safety Improvement Act of 2008 (RSIA) requires that certain railroads implement PTC to prevent train-to-train collisions on certain rail lines by the end of 2015. The FRA states that the technology is also capable of preventing: over-speed derailments; casualties or injuries to roadway workers (e.g., maintenance-of-way workers, bridge workers, signal maintainers) operating within their limits of authority as a result of unauthorized incursion by a train; and train movements through a switch left in the wrong position.

PTC is intended to become an integral part of the signaling and train control system on the mandated railroads, says Paul Mosier, rail and transit operations planning manager for Parsons Brinckerhoff (PB). "The objective of applying PTC is to ensure that you have a system in place that would provide a high level of confidence, almost a fail-safe level of confidence, for train separation," he says.

Today, train separation is highly dependent on the locomotive engineer, the operator, and their compliance with the operating rules and what the operating rules instruct them to do based on the indication that they see on the signal. "It's no different from you or me driving our car," Mosier says. "The burden of safety in terms of the operation of the train and stopping the train in today's world is largely on the shoulders of the operator of the train."

PTC will essentially remove the human intervention factor from the equation of making sure that trains stay safely separated. The system will constantly update itself as to the location of the train, with respect to a slower speed indication or a stop indication coming up ahead, and it will be calculating what the safe braking distance is to get to that point, Mosier says. "If the train violates the speed that would allow it to either slow down or come to a stop at the point ahead, then the system takes over and will automatically slow the train down or stop it."

With this technology, the signal blocks are now integrated in the train control system, which conforms to a braking distance that is congruous with a human operator. Another attribute that will change is the lengths of the signal blocks. "Those signal blocks will have to be lengthened, so you'll have an additional margin of safety," Mosier says.

Interoperability

Beyond the challenge of meeting the deadlines, Mosier says that field installation will also be an issue. "But, many [rail systems] have already gotten well into the process with procurement, they've been interacting with the vendors that provide the technology, they've been interacting with the contractors that can do the installation."

For rail entities that share track, ensuring interoperability — between the different technologies and systems that may be employed — is key. "Because at the end of the day, it's almost a systems integration challenge to be certain that a system that works on a Norfolk Southern is capable of moving locomotives and cars that would be coming onto their system from CSX, for example," Mosier says. "The same could be said of the cars from BNSF and Union Pacific, because the railroads have track rights where they can operate on each other's tracks, so compatibility has been a priority for the rail systems."

Interoperability will also play a role in the PTC project PB has undertaken for California commuter rail line Caltrain. The company is the technical lead for ensuring interoperability between the train control system (CBOSS) being developed by the Peninsula Corridor Joint Powers Board to meet the 2008 PTC mandate and the PTC systems being deployed by Union Pacific and Caltrain's tenant operators. PB is providing the project manager and project engineer, as well as operations, signal engineering resources and system safety support to the project.

The project is intended to provide all passenger trains operating on Caltrain's San Francisco peninsula with in-cab equipment and also supported a successful waiver application to the FRA for the operation of lightweight electrical multiple unit rolling stock, Mosier says. CBOSS will also support run-time improvements and improve the operation and safety of the 64 highway- and pedestrian-grade crossings currently in operation.

Other possible PTC projects in the works include the development of a  PTC system simulation. "There have been some discussions to do a simulation of a conceptual design for a part of a rail system, with the attributes of PTC versus the fixed-block type of signaling system that is out there today," Mosier says. "The models are built from anything from preliminary engineering detail drawings to as-built drawings for existing infrastructure, and that includes the tracks and the switches.

"The results are probably as close as you can get to replicate the performance of a rail network without actually being out on the railroad," Mosier says. Typically, these models are used to test future service levels to determine what modifications need to be made in the infrastructure to provide capacity for growth and those sorts of things, he adds.


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