From my understanding the radio chatter works like your standard walkie-talkie system, where if one person is talking, you can't talk. So if somebody was active on the radio, then it is highly possible that he wasn't able to communicate. From this view I think that they should do some major upgrades to the communication system to a system that allows people to talk at the same time, my high school theatre had a communication system (Clear-Com) that allowed us to talk at the same time as others, which allows you to essentially tell somebody over the air to "shut-up" (as bad as it seems wording it this way) if they are talking and something is about to go wrong.
Now this is just my view and I am sure that there are several reasons why not to have it, and I am also sure that it is difficult to design over a system so large, but I think that they should have a 2-mode E-Stop system. I have no idea how they would go about designing this, but have 2 buttons, one that will E-Stop and brake your train, and a second button that when engaged will E-Stop all trains, on all lines, possibly shutting down power to the entire system (and have these buttons on more than just the trains, platform control stations as well). This way, if a driver of one train (or a CM on a platform) sees something catastrophic about to go wrong, instead of having to radio (which may be busy) and inform the correct person of the error, which would also include a reaction time, they could punch this button and have all trains immediately stop where they are. In this situation Austin could have hit this button and stopped pink immediately and have prevented the crash, rather than having to potentially wait for the radios to free up, communicate to the other driver, have the other driver react to the communication, and then stop their train.
I know that there are probably some major complications and cons to having a "kill-all" button, but it would have prevented something like this from happening.
