The primary lesson is that "safety is of the first importance, obedience to the rules is required". This does raise the question to me of why we haven't, with our computers, gps, and communications, come up with a more universal system of in-train signals, and a 21st century version of ATS? Positinve Train Control will supposedly do this? Automatic Train Stop mechanisms and in-cab signaling are a good idea on all rail passenger systems. It would add to the safety of any system, including SMART.

Before jumping to a lot of conclusions, there's going to be an NTSB investigation. There are a few glaring questions still to be answered by the NTSB investigation. The Metrolink Engineer purportedly ran an abolute signal displying a red aspect at CP Topanga.

Was the UP Train in the block, as well? This would have caused a red aspect, if the signal was working properly. Was the switch at CP Topanga lined for the approaching UP train to enter the double track and pass the Metrolink Train? If this was the case, not only did the ML Engineer run the signal, he also would have run through the switch. Did he?

If this was the intended movement, and the switch was not aligned, why not? This would mean that the move had not been set up and the Engineer may not have entered Chatsworth on a yellow signal, and not been expecting a red at CP Topanga. (Between the time the ML train stopped, and left, the UP may not have entered the next block, would be one explanation for the ML Engineer having a green entering Chatsworth, as well?)

If the switch was aligned for the UP train, the ML Engineer would have recieved a yellow signal aspect arriving into Chatsworth, indicating that the next signal was red, and/or that the switch was lined against him. Upon leaving the Chatsworth station he would have been required to operate expecting a red signal at CP Topanga, and prepared to stop short. Did he have a yellow signal entering Chatsworth? Did he leave Chatsworth in a way that indicated that he was approaching the next signal with caution?

The communications and status of the signaling equipment will also be scrutinized. This has been a factor in a few head on collisions. And, with newer technologies, there are sometimes new things that can go wrong.

Then there is the level of "experience" in the Engineer? How long, what record? What training and orientation on this run? It's going to be at least a few weeks before we have the answers to these questions. And, when we do have answers to these, and about a few hundred others that they are going through right now, we'll be better able to judge what lessons apply. Every rule in the General Code is purpotedly written because of an accident.

All losses are tragic in these cases. And, a few of the gainsay element will try to use these tragedies to stoke fear and prey on popular ignorance for political points. Of course, you're still about a thousand times more likely to be killed driving to work on the 101, and that could be improved on a lot, too.