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New to the forum. I have loved trains my whole life but just now taking the time to really understand them and watch them/photograph them. I don't have any fancy camera so excuse the quality. One thing I'm reading up on are the signals and their meaning. I'm still confused (maybe because I haven't gotten to that part of the text) on the meaning of two signal heads on one pole. Is is strictly to give them the ability to run a yellow over read for it's appropriate meaning for example or does the top signal designate what the operator needs to know about one track and the bottom is for another track?
I get confused when reading text and looking over the BNSF railway signal aspects and indications manual because their example signals look like search light signals to me which I have yet to see in my area (Marysville) so I am having trouble relating those diagrams to our typical "darth vader" signals we have now-a-days since (for example, in the SOP it shows a diverging clear signal has multiple possibilities but all are consisted with green being middle or bottom when the darth vader lights only have green on top of signal head. Anyways...help would be appreciated to clear this up.
Here are some pics. These are from Lowell in Everett.
More from Lowell. It's a nice spot for different angles. Just wish it was spring or summer, dormant vegetation looks horrible. Snuck two pictures from Delta yard in Everett.
I'm still confused (maybe because I haven't gotten to that part of the text) on the meaning of two signal heads on one pole. Is is strictly to give them the ability to run a yellow over read for it's appropriate meaning for example or does the top signal designate what the operator needs to know about one track and the bottom is for another track?
I'm no expert but here goes a simple version. If this is incorrect, I'm sure a real railroader will speak up and correct me!
A signal indicates the status of the next block of track.
If there is only one signal head, that means the next block of track does not any turnouts - there is only path for the train to take in that block.
If the block of track past the signal has a diverging route, say a crossover from one main to another, then there will be two signal heads.
The top one indicates the status of the straight path.
The bottom indicates the status of the diverging path.
For example, say there are two mains - Main 1 and Main 2. There is a signal bridge over the tracks. There are two signal heads over each track. Just past the signals are crossovers between the two mains.
If the signal over Main 1 shows a green on the top signal head and a red on the bottom one - that means the train is clear to proceed and will stay on Main 1 (the straight path) in the next block.
If dispatch has lined the crossover switches to have the train go from Main 1 to Main 2, then the top signal head over Main 1 would show red and the bottom one green. That would be "Diverging Clear", meaning the train is not authorized to take the straight path (Main 1) but is authorized to take the diverging path (the crossover to Main 2).
The same would go for other the other aspects. You can have "Approach Medium" (flashing yellow over red) or "Diverging Approach Medium" (red over flashing yellow), etc.
It is common to have two signal heads at intermediate signals where the signals do not govern movement through a turnout. Generally these installations are at the approach block to a siding or other control point. Here's an example of how the two heads are used:
Train 1234 South is 4 miles from the siding at Anna and will meet Train 2345 North at Anna. If 1234 South is going to hold the main, the intermediate signal two miles out from North Anna will display flashing yellow over red (Approach Medium) and North Anna will display yellow over red (Approach) until 2345 North is in the clear at South Anna.
If 1234 South is going in the hole, the intermediate will display yellow over yellow (also Approach Medium on BNSF, Approach Diverging on UP and some divisions of BNSF) and North Anna will display red over yellow (Diverging Approach) until 2345 North is clear of South Anna.
Here are some from today in Mukilteo at MP 28. I was hoping the time I was there it would be busy but signals went dark for a while so I left. Of course when I couldn't stop to take pictures Marysville picked up. Oh well.
Getting kind of tired of Lowell from a photography stand point but it gives me an idea on what is coming and going from Snohomish. I have a slight obsession with the Grinstein Green macs so this consist was not too exciting for me.
I saw 3 CREX engines on three different trains today. I'm still trying to learn all the train talk on the radio so I know where people are going and coming from but it's slow going. Followed the oil train to Skykomish. I think he conductor did a double take when he saw me in Skykomish after seeing me in Lowell. Haha.
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