8th Notch wrote:Patrick Boylan wrote:
http://usnews.nbcnews.com/_news/2013/12 ... in-ny?lite" onclick="window.open(this.href);return false;
Sources told NBC News late Sunday afternoon that the train's engineer — a "respected veteran" with 20 years of Metro-North experience who suffered minor injuries — claimed when first responders arrived that he hit the brakes as the train approached the turn.
Sounds like more speculation again to me.... As stated we don't know any of the facts! We are all human and regardless of how many times the track was traveled by the engineer he still could have not been paying attention or lost situational awareness. Obviously as a railroader we are all hoping for his sake that it wasn't human error however as humans we are all subject to it in some way shape or form. The control car does not send a signal to the locomotive telling it it to apply the brakes on the train, it is done pneumatically from the brake valve in the control car itself. Not a knock against anyone but like Dutch said only non experts think push pull is unsafe and I think that is because many do not know how it works. If a train derails and goes into emergency it also trips a pneumatic control switch which in turn knocks down any power being supplied from the loco.
I hope you meant we don't know ALL the facts, not that we don't know ANY. We know some of the facts. It's a fact that some reporter said that some sources said the engineer said he hit the brakes. It's a fact I know from looking at the pictures that the entire train came off the tracks without tearing up the tracks as much as the New Haven line's derailment and sideswipe did.
I also know that the control car pneumatically controls the brakes, but that's just another way of sending a signal, whether it's electronic, pneumatic or carrier pigeon. Turning a handle in the cab car is supposed to apply brakes throughout the train, or apply brakes in the locomotive only, and another handle is supposed to control the throttle.
The further away the handles are from the things that they're supposed to control, the more likely it is that something will go wrong.
Yes, if a train derails and goes into emergency it trips a pneumatic switch and the locomotive's supposed to stop pushing, or pulling, and all the brakes are supposed to go on. But if there was a problem with the system in the first place MAYBE, and yes this is speculation, the engineer didn't get the brake application he was expecting, and so the train didn't slow down the way it should have BEFORE it derailed. And if the locomotive's at the back you've added several extra connection points between the control stand and the locomotive.
Haven't we all heard of cases where the last few cars in a freight train didn't apply their brakes because of cumulative air line problems? So what happens if there's a bit of blockage in the air line from cab car to locomotive, can it keep the cab car's brake valve from sending a proper signal to the locomotive? And vice versa, does trying to apply trainline brakes from the locomotive ever have trouble getting all the cars to apply brakes? What brake did the engineer try to apply, locomotive only, or brakes on the entire train? I don't have these facts, for all I know the engineer might not be able to choose locomotive brake only, maybe this equipment has some fancy stuff that tries to decide for the engineer what the best blend of locomotive and train brake is.
DutchRailnut wrote:The real experts seem to believe push-pull is safe, as today 35 000 trains a day are operated this way and testing by international agencies and domestic NTSB do seem to suggest that push-pull is safe.
only non-experts seem to think its un-safe !!
Dutch, I haven't said that locomotive on the rear is more dangerous than in the front, I've only said I wonder, and despite you saying it twice just the fact that "everybody does it" means a lot less than the testing you say has been done.
I do find Mbta fan's example interesting, where locomotive in the rear may have been a mitigating factor in that rear end crash.