Western Railroad Discussion > What Does Yellow Over Yellow Mean?

The reason I ask is because not long ago on a return trip home to Tulare northbound from LA on the 99, I caught up to and subsequently passed a short train also heading north. This was late at night on the 99 freeway just south of Famoso. In fact, I believe this is the last northbound signal (old SP double head target type) before reaching the turnoff for the remaining stub branch of the former Exeter Sub. I'm not educated in railroad signalling, but doesn't a lower light indicate a diverging aspect? I mean if it was yellow or green over red, that means the train is going to continue forward. But doesn't anything yellow or green on the lower mast indicate that you are about to turn off? Was this train destined to head up the old branch towards Hollis?

Des-Lab Wrote:
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> The reason I ask is because not long ago on a
> return trip home to Tulare northbound from LA on
> the 99, I caught up to and subsequently passed a
> short train also heading north. This was late at
> night on the 99 freeway just south of Famoso. In
> fact, I believe this is the last northbound signal
> (old SP double head target type) before reaching
> the turnoff for the remaining stub branch of the
> former Exeter Sub. I'm not educated in railroad
> signalling, but doesn't a lower light indicate a
> diverging aspect? I mean if it was yellow or green
> over red, that means the train is going to
> continue forward. But doesn't anything yellow or
> green on the lower mast indicate that you are
> about to turn off? Was this train destined to head
> up the old branch towards Hollis?

The meaning of Y/Y is probably the most variable of any signal aspect in existence, and depends on which rulebook applies.

As a general rule of thumb, though, a bottom light lit other than red does not NECESSARILY mean a diverging route will be taken at the next signal. A bottom yellow or green almost always* DOES indicate a diverging route when the top light is red, but a Y/Y or Y/G can be used as a "second yellow" on lines where signals are close together and/or there is lots of traffic at running at main line speeds.

Underlying this question is whether the applicable rulebook uses route signalling or speed signalling. I believe the SP used route signalling, and I believe under its rules the Y/Y you saw probably did indicate a diverging route at the next signal. But Norfolk Southern -- to provide a conflicting example -- uses route signalling and would normally use Y/G (Approach Diverging) for that purpose whereas it uses Y/Y as Advance Approach (proceed prepared to stop at the second signal).

*-The only common exceptions I can think of are R/Y, R/R/Y, R/L, or R/R/L for Restricting. And R/Y can also be Medium Approach, depending on whose rulebook is in use. Ask the Amtrak engineer on the Pere Marquette who crossed that up last year for an example.



Edited 1 time(s). Last edit at 11/17/10 14:05 by toledopatch.

Approach Diverging, maybe? Ours our yellow over green. Something like proceed on diverging route at next signal at prescribed speed through switch.

Des-Lab Wrote:
-------------------------------------------------------
> The reason I ask is because not long ago on a
> return trip home to Tulare northbound from LA on
> the 99, I caught up to and subsequently passed a
> short train also heading north. This was late at
> night on the 99 freeway just south of Famoso. In
> fact, I believe this is the last northbound signal
> (old SP double head target type) before reaching
> the turnoff for the remaining stub branch of the
> former Exeter Sub. I'm not educated in railroad
> signalling, but doesn't a lower light indicate a
> diverging aspect? I mean if it was yellow or green
> over red, that means the train is going to
> continue forward. But doesn't anything yellow or
> green on the lower mast indicate that you are
> about to turn off? Was this train destined to head
> up the old branch towards Hollis?

If you say it's former SP (and I'm assuming current UP) it is approach diverging. It means proceed prepared to advance on diverging route at next signal. It's just a heads up that at the next signal, you will bs taking a diverging route, whether that be crossing over to another track in multiple main track territory or taking a siding in single track territory or diverging off on another line at the next control point.

It means "Advanced Approach." Approach the next signal at Medium Speed
prepared to stop at the second signal. At least it did. cf7

cf7 Wrote:
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> It means "Advanced Approach." Approach the next
> signal at Medium Speed
> prepared to stop at the second signal. At least it
> did. cf7

Which rulebook are you citing this from? As I explained earlier, Y/Y does not mean Advance Approach on all railroads.

... or per the UP/Amtrak/old SP. prepare to go through a diverging route switch at the very next signal (aka "Approach Medium" on some other RR's).


The original asked question is another reason to own (and support) Altamont Press with it's various timetables and useful information - the past 20 printed California Region timetables come to mind. All the info you want to know and more on not just the ex-SP Fresno and ex-SP Exeter Subs but a complete center section (in color) extensively covering signal aspects (over a dozen different aspects), all the California Class 1 and Shortline subdivisions/branches and even useful maps to boot:
http://www.altamontpress.com/

Seeing Altamont Press is now unfortunately set to go out of business, this thread is exactly why good causes that support/reward the railfan community are disappearing. Kind of a shame...



Edited 1 time(s). Last edit at 11/17/10 15:04 by espeeboy.

espeeboy Wrote:
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> ... or per the UP/Amtrak/old SP. prepare to go
> through a diverging route switch at the very next
> signal (aka "Approach Medium" on some other
> RR's).


Union Pacific
Rule 9.2.5 - Approach Diverging
Proceed prepared to advance on diverging route at next signal at prescribed speed through turnout.

HB

Advance approach medium, on the New York Central's 5 block separation system....

pdt Wrote:
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> Advance approach medium, on the New York Central's
> 5 block separation system....

I thought that one was G/Y.

Almost every railroad has their own meaning for different signals...

On Union Pacific it is Approach Diverging, as quoted above.

On BNSF (The other major class I up in Des-Lab's area) it's Approach Medium, which means proceed prepared to pass next signal not exceeding 40 MPH and be prepared to proceed on diverging route not exceeding prescribed speed through turnout.

On the BNSF it is Approach Medium which basically means proceed prepared to pass next signal not exceeding 40 MPH and take the diverging route a the prescribed speed through the turnout. A flashing yellow also means the same thing.

What they have been doing is this, the Yellow over Yellow is placed at the approach signal to a control point and you will be taking the diverging route at the next signal ie, crossing over or entering a siding. However if that same signal is flashing yellow over red, then that means your following a train 2 signal blocks ahead.

Santa Fe

Seen that signal on NS, means Advance approach.

imrl Wrote:
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> If you say it's former SP (and I'm assuming
> current UP) it is approach diverging. It means
> proceed prepared to advance on diverging route at
> next signal. It's just a heads up that at the next
> signal, you will bs taking a diverging route,
> whether that be crossing over to another track in
> multiple main track territory or taking a siding
> in single track territory or diverging off on
> another line at the next control point.

I saw this just last night at Paxico, KS on the Golden State route and wondered the same thing.

In Canada, it is CROR Rule 408, Clear to Slow,(Approach Slow)... Proceed , approaching next signal at slow speed (15 miles an hour), usually for a turnout... the next signal would be "Slow to clear" (Slow Clear) or "Slow to stop" (Slow approach)

On Caltrain, we have two definitions fot yellow over yellow. In route signal territory, it is approac diverging, same as UP. In speed signal territory it means approach slow, be prepared to pass next signal at slow speed(20 mph for passenger).