The federal rail safety program for Positive Train Control (PTC) on the Class 1 freight rails in North America mandates that each train be tracked, and that no trains may travel on a track without its location being known. The U.S. Rail Safety Improvement Act of 2008 passed shortly after the deadly commuter rail accident in Los Angeles. Details of the technological hurdles were discussed in a session at the 2010 Trimble Dimensions Conference.
There are significant technological hurdles for the railways to address before compliance with PTC becomes mandatory in 2015. The requirements of the system are to prevent an over-speed through automated engine controls, to avoid signal authority violations, to protect track crews, to prevent movement through a switch even if it is in the wrong position, and to know the location of every rail asset within 2.2M of horizontal accuracy and 0.8m vertical. Achieving the location requirement is a difficult task given that the accuracy requirement is below today’s mapping-grade GPS, and the PTC requirement specifies that the location of all assets must be maintained to 100% accuracy.
To meet these requirement, the four major Class 1 North American rail companies have banded together to specify guidelines for an interoperable system, and each is actively surveying all of their assets. There are hurdles here due to an old hierarchical structure that has divided operations by asset class, with departments for Signals, Track, Locomotives, etc. Each asset operation has been responsible for recording their own details, including the location of the asset, and the accuracy of those positions vary widely.
Surveying the entire tracks of each railroad to assay all assets is a considerable project, given the miles of track, and the by-and-large non-technically savvy crew. CSX, one of the major East coast operators, has devised a plan that involves a mobile handheld GPS data collector and a custom program that was created jointly by Trimble and Esri. The solution was built with both the ArcPad and Trimble Mobile Tools Field SDK, and contains rigid processing rules, relying on differential correction to achieve the necessary accuracy.
The railroads are using a breadth of different geospatial tools in order to meet this mandate. On the survey side are mobile solutions, such as described above, as well as LiDAR data collection all along their tracks. LiDAR provides the detail and accuracy to verify field data collection, and is also a good enough accuracy for cataloging a large number of the assets.
This aggressive mandate of Positive Train Control is speeding along many geospatial advancements due to the challenges that it poses. All the tools and technology to make such a system are available, yet the mandate pushes the boundaries in terms of both the scale and accuracy that are required, as well as the communication and coordination between multiple competing companies. There are still five more years to go before the mandate must be met, and I’m certain we’ll all be hearing much more about the challenges and solutions in the intervening years.
