kd_1014 wrote:Gotcha, Thanks so much. I understand why it would display a Clear or Stop indication, because just west and east of those signals is a fixed approach signal, which I would assume you need to get track authority to proceed over the diamond, which means you need to stop. Thanks for the info!
The signals at the diamond at Fuller on the GRE only govern that interlocking plant alone - outside of the signals, they mean nothing. To the west it is all yard limits so the crews move at restricted "don't hit anything" speed and are on the lookout for anything they might hit. Not sure but I'm willing to bet the yard limits go all the way to the C&M property line just west of Alpine.
Headed east, there may be more yard limit territory for a short distance but at some point it's all track authority to Lowell, so they get written orders from a dispatcher.
The approach signals to Fuller on the GRE side are just approach: they'll show approach indications if the diamond is not lined, and clear indications if they are lined over the CSX, regardless of what is in the block between the approach signals and the junction itself.
Of course on the CSX side it is all CTC controlled, south of the southward absolute signals (SAS) at the diamond. To the north of those signals, it is also track authority, and the signal at Turner Street is an approach signal to Fuller Jct that acts in much the same way as the ones on the GRE side. However at some point a couple years ago its behavior changed. Used to be stop when something was lined north at Fuller, approach when nothing was lined at Fuller, and clear when there was a line-up south across Fuller. Now the signal is red except for when there is a line-up at Fuller heading south, at least based on my observations.
As for the absolute mast signals at Fuller all having two heads, it has long been the tradition of CSX's predecessors, and continues to be the case today, that all absolute signals have two heads, regardless if they're necessary or not. For the ones at Fuller, they need the bottom head to display a restricting indication, which is red over yellow, and possibly others, I have never fully looked into the signal/route logic at that location, and it may have changed once Watson was eliminated over a year ago. Today CSX still does 2-head absolutes, by choosing to hang the lunar white lamp on the second head with another red lamp, but according to the signal rules, having all four colors on the top head would technically be legal in that sense. Sometimes, traditions die hard, and there is an argument to be had for having two lamps on absolute masts, in case one burns out so that there is more likely to still be a signal of some form displayed - at least to mark the spot as a visual reminder. It's easier to pass a dark signal than one that is improperly displayed, but at least lit "somehow".