September, 2008. A Metrolink Train and a Union Pacific ballast (rock) train had a head-on collision in Chatsworth, Ca. It was later determined that the engineer was involved in a text messaging session which possibly distracted him.
See
http://en.wikipedia.org/wiki/2008_Chatsworth_train_collision
I've been to that site several times as part of the investigation, and the UP crew only had 4.5 seconds from the time they saw the passenger train to collision. Had is not occurred on an 8° curve, the death tool would have been much higher. 25 deaths caused the FRA to mandate PTC to be instilled by 2015.
Metro North is NOT required to install this as they do not meet the criteria set forth in the law.
PTC is GPS and railroad network based. The major headache is really the integration of the system over the 4 major class I railroads (UP, BNSF, CSX and NS), so that locomotives may traverse other company's property seamlessly without the need to switch locomotives when on another railroad's track. Getting th railroads to agree on a standard was a huge undertaking.
They
are behind schedule, but not as badly as one would expect.