Western Railroad Discussion > Signal Sunday..

BNSF 7099 east approaching the CA Hwy 138 overpass near Pine Lodge, CA on 10/12/2019. But why is track 2 displaying yellow over green? There was a westbound coming, but wouldn't the lower signal be a diverging signal to main 3? 

Tom



Edited 2 time(s). Last edit at 03/26/23 13:26 by Railfan4Christ.

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Very nice photo!  The yellow over green is a "Advance Approach" on the BNSF.  Its means "Proceed prepared to pass next signal not excedding 50 MPH and be prepared to enter diverging route at prescribed speed".

Normally you might see a Yellow over Yellow (Approach Medium) for an upcoming diverging signal.  However, that aspect requires a train to slow to 40 MPH and then enter the divering route at whatever speed the switch requires.  Since the turnouts at CAJON are good for 50 MPH, there is no need for a train to slow to 40 MPH to then take a turnout at 50 MPH.  So the Advance Approach allows a train to only slow to 50 MPH.  Most likely the dispatcher is switching the train to Main 3 at CAJON but its possible if the oncoming train is short enough the dispatcher has already lined the train to Main 1....but this is doubtful.

NOTE:  There is also an aspect for 60 MPH turnouts (which are relatively rare) and its a Yellow over Flashing Green (Approach Limited).

SCAX3401 Wrote:
-------------------------------------------------------
> Very nice photo!  The yellow over green is a
> "Advance Approach" on the BNSF.  Its means
> "Proceed prepared to pass next signal not
> excedding 50 MPH and be prepared to enter
> diverging route at prescribed speed".
>
> Normally you might see a Yellow over Yellow
> (Approach Medium) for an upcoming diverging
> signal.  However, that aspect requires a train to
> slow to 40 MPH and then enter the divering route
> at whatever speed the switch requires.  Since the
> turnouts at CAJON are good for 50 MPH, there is no
> need for a train to slow to 40 MPH to then take a
> turnout at 50 MPH.  So the Advance Approach
> allows a train to only slow to 50 MPH.  Most
> likely the dispatcher is switching the train to
> Main 3 at CAJON but its possible if the oncoming
> train is short enough the dispatcher has already
> lined the train to Main 1....but this is
> doubtful.
>
> NOTE:  There is also an aspect for 60 MPH
> turnouts (which are relatively rare) and its a
> Yellow over Flashing Green (Approach Limited).

Thank you for clearing that up!

Tom

Very NICE with train and signals!

Larry

SCAX3401 Wrote:
-------------------------------------------------------
> Very nice photo!  The yellow over green is a
> "Advance Approach" on the BNSF.  Its means
> "Proceed prepared to pass next signal not
> excedding 50 MPH and be prepared to enter
> diverging route at prescribed speed".
...
> NOTE:  There is also an aspect for 60 MPH
> turnouts (which are relatively rare) and its a
> Yellow over Flashing Green (Approach Limited).

THANKS for this response. It's really informative and points out a use for signals that I thought were becoming redundant. They can be used as real time speed limit signs and changeable ones at that. Humans make the best engineers in most situations and these indications bring the engineer to the level of the computer, but with the added benefit of situational awareness no machine can match.