Okay, a really brief primer on PTC:
1) It is NOT "billions of dollars more costly" than what railroads are doing now. In fact, railroads are spending to replace existing CTC (with new CTC, same functionality) at a rate of $500 million or so per year (the number is from railroad R-1 reports to STB). Over the next 20 years, at that rate of spending, railroads will replace all the existing signal systems on the 65,000 route miles of signaled track -- for a total cost of more than $9 billion.
2) Replacing the CTC with PTC instead would cost less than $8 billion (these numbers are from a cost/benefit analysis I did for FRA in 2004, and which went to Congress).
3) PTC, whether "overlay" or replacement, is functionally the equivalent of a cab signal system, since it enforces movement authorities (hence "positive" in the name). As such, it would allow railroads to operate at higher speeds -- on Class V track, 90 MPH for passenger trains.
4) FRA has written implementing regulations for PTC -- that was done about three years ago.
5) This is NOT an "unfunded mandate" (notwithstanding Mike Ward's reference to it as such at a conference last week). No, the improvement in safety won't justify it, but does it really need justification if it's cheaper than replacing the existing control system?
6) The equipment needed for PTC can also provide information that can be used to better manage the railroad, allowing for greater capacity, better equipment utilization, more efficient scheduling of time on track for work gangs -- these benefits are substantial. In the 2004 report to Congress, they were estimated at more than $2 billion *annually*.
See
http://www.tsd.org/papers/FRA%20PTC%20f ... -16-04.pdf