Wow! I'm trying to catch up on all this reading but there's just soooo much. Very tragic all the way around.
The husband and I have talked a lot about the accident. Knowing the safety features that are in place (MAPO, etc.) it's hard to fathom that something like this could happen. In fact, when I was at WDW with my brother and his daughters in May the youngest of my nieces was afraid to ride the monorail. I assured her there are safety systems and proceedures in place to prevent accidents from happening. I told her it was impossible. When we first heard of this accident we were sitting in the airport in Atlanta waiting for our flight.
In another thread it was stated by a former monorail pilot who was told by friends who are still cast members there that pink had overriden or disengaged (not sure which) their MAPO and was reversing. Many pages ago in this thread another poster said that even though pink had overriden theirs that purple's MAPO should have put his train in an e-stop or at least alerted that pilot that another train was too close. Also, in another thread (the one from 2002 where a monorail pilot was discussing the MAPO system) it was stated that once the trains are within 10 feet of each other they no longer "see" each other, it's as if the other train isn't there at all. Some people are assuming that there was a MAPO system failure. Here's our thoughts (and it's purely speculation on our part): we feel like this is not a system failure, it's human error. If pink disengages it's MAPO would it not make it virtually "disappear" within that system? I don't know if that's exactly how it works but it makes sense that this could be a possibility. That could explain a lot. So in theory: pink has disengaged and is moving in reverse, purple's MAPO never "saw" the now "invisible" train coming at it, the 10 foot proximity also tells us that the trains are now "invisible" to each other, and a newer, less experienced pilot who is working some crazy late hours has very little to no time to react. Also, there's a lot of discussion as to which train was moving. Was pink still moving backward? Was purple stopped? Was pink stopped? Was purple moving forward? The theory that pink's disengaged MAPO still could work even if it wasn't in motion. Perhaps pink was stationary but had not yet re-engaged. The monorails don't stop on a dime. Purple could have still run right into it if it didn't know it was there. These are just our thoughts. It's tragic all the way around. I'll be very interested to find out exactly what did happen. If the NTSB is investigating there will be a report and those reports can be read.
My hubby seems to think this will be the end of riding in the front of the monorails with the pilots. I disagree. What do you think?
Overriding the MAPO does not "turn it off" or "make you invisible"
At certain points on the line, the MAPO signal is generated. Each train looks for that signal comming to it from the direction it is travling. In fact it looks for multiple signals. When it sees those signals, it knows the path is clear. Certain things can block those signals - an open switch, a denergized section, or an other train.
When the train sees two or more signals comming to it, it knows there are at least two clear sections ahead of it, and its green
When it sees only one signal, it goes amber, which is in essence saying "I see one clear section ahead, but beyond there there is some problem"
When it sees no signals it stops because it says "I cannot verify this section is clear, I am stopping"
Overiding the MAPO just tells the train "Look, I know there is no signal comming, but there is a reason for it, so now lets move"
The train continues to block the MAPO signal and other trains will continue to see it.
I am not a CM, nor was I ever one, but this is how it was explained to me a number of times. It is also how a block light system works on other rails
One thing to remember is, no matter how many safety interlocks you install and how tight your procedures are, there is always the chance for that freak perfect storm of events to happen where the system fails. I am not saying that is what happend here, or making any sort of call on if the current system was robust or not. I am just saying, I write Methods and Procedures for a living. And you sit down, try to think of everything, vet the procedure with the field, do field trials, re-write the procedure, and then finally release it - after plenty of due dilligence, and then a month later you get a call because someone has hit a situation you never though of.
I truly feel badly for all the people involved. It must be a horrible feeling to know that you were involved in a situation that caused the death of a person - and caused such damage and had such an impact as well. Even if you did nothing wrong and "did things by the book" that event is going to hang over you for a long long time.
-dave