PTC requirements…
http://www.fra.dot.gov/roa/press_releases/fp_FRA%2017-12%20.shtml
Should be the first one listed.
The original requirement was to install PTC on any track that carried TIH traffic in 2008. At the same time, another arm of the FRA was requiring rerouting of TIH traffic to the least-risk routes. So, the PTC legislation would have required PTC on some routes, that by 2015 would no longer have any TIH traffic on them. This removes the requirement that these routes be equipped.
A common sense change that took several years to get done…
What the industry really needs is a relaxed, phased implentation, say 20% of the route miles each year for 5 years starting in 2015. That would give a chance to work through hardware, software and scalability issues that are sure to crop up.
The biggest problems are in crowded metropolitan areas where you have many routes in close proximity. The issue is having the on-board equipment poll and react to the correct wayside equipment. For this you need plenty of data frequencies, since if adjacent routes share frequencies you can have conflicts.
They can all work on the same set of frequencies, in the same way as a wireless access point operates at an airport or other such facility. It’s the addressing that’s important.
GPS resolution is the bigger issue where proximity is concerned.