US colour light signals - quick query

[melmerby]

Hi all

Looking at Virtual Railfan camera one see many various signal systems in use but I have a query about the Pennsylvania to Harrisburg line used mainly by Amtrak electrics

At Paradise (on the VR camera) you can see the northbound colour lights controlling crossovers. They are the double light type that mimic a UQ semaphore arm's position.

When a train passes the signal on green the lights change to red and shortly after a white light below the main head illuminates until the next signal is passed when they change to yellow and the white light goes out.

What is that white light for?

 

At Deshler OH crossing the N-S route has similar signals but the white lights there seem to have a different purpose as they are illuminated before the train passes and extiguish immediately the aspects change from red.

 

 

[Andy Reichert]

You need to find articles on US proto and model signalling by Dr. Bruce Chubb.

 

Also there is a signalling elist write to: railway-signaling+owner@groups.io

 

Model computer control and signalling systems that automate it: "CMRI" and" JMRI"

 

Andy

[Grovenor]

Generalif the top head is red, or horizontal and the lower head has a single white marker light then it means 'Stop and Proceed,

A search of Google can bring up lots of US signalling rules.

A quick guide to Northeast corridor aspects here https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=13&ved=2ahUKEwjOovTtybPmAhXBiVwKHf2JCPAQFjAMegQIBBAC&url=https%3A%2F%2Fsteamcdn-a.akamaihd.net%2Fsteam%2Fapps%2F65232%2Fmanuals%2FNortheast_Corridor_Signal_Guide.pdf&usg=AOvVaw3DHFaoZYp2Y6hEyQuHXCr2

 

[mdvle]

2 hours ago, melmerby said:

At Paradise (on the VR camera) you can see the northbound colour lights controlling crossovers. They are the double light type that mimic a UQ semaphore arm's position.

When a train passes the signal on green the lights change to red and shortly after a white light below the main head illuminates until the next signal is passed when they change to yellow and the white light goes out.

What is that white light for?

 

At Deshler OH crossing the N-S route has similar signals but the white lights there seem to have a different purpose as they are illuminated before the train passes and extiguish immediately the aspects change from red.

 

 

 

One of the things possible in North American railway signalling is the ability to indicate that the engineer can proceed past a red signal, though with the condition that the engineer must be able to stop the train in time if they catch up to the train in front (though the rules are likely more explicit in the conditions).  In Canada the rules use a letter attached to the signal to indicate what the red light means, it is possible in your example they are using a light.

[BR60103]

The rules usually have a line about the speed "being able to stop within half the range of vision".

[Johann Marsbar]

This is a very useful site for signalling matters...

https://www.railroadsignals.us/

 

.

[melmerby]

10 hours ago, mdvle said:

 

One of the things possible in North American railway signalling is the ability to indicate that the engineer can proceed past a red signal, though with the condition that the engineer must be able to stop the train in time if they catch up to the train in front (though the rules are likely more explicit in the conditions).

I wonder what it is used for?

These signals only show a white just after a train has just past.

At other times they spend long periods set to red.

There are also subsidary signals for changing tracks at this point, a pair of angled yellows on a bracket of the main post, which only illuminate for a train changing tracks, the main head staying red.

These are used for the local NS freights.

 

[dave1905]

Different railroads can have different signal systems based on the preferences of the previous owners.  For example the Phillie-Harrisburg line was former PRR.

 

Under NORAC rules that cover that area:

Two greens vertical are Clear, rule 281, proceed not exceeding Normal Speed

Two yellow diagonal with a white light below them are rule 286, Medium Approach, proceed prepared to stop at the next signal, trains exceeding medium speed must begin reduction to Medium Speed as soon as the Medium Approach signal is clearly visible.

Two yellow diagonal are rule 285, Approach, proceed prepared to stop at the next signal.  Trains exceeding Medium Speed must begin reduction to Medium Speed as soon as the engine passes the approach signal.

 

The Medium approach requires the train to begin reducing to Medium Speed as soon as the signal is visible and the Approach allows the train to begin reducing to medium when the engine passes the signal.  

 

A signal with a red horizontal signal above a yellow diagonal signal, depends whether the diagonal is slanted NW-SE or SW-NE.

SW-NE yellow is rule 288, slow approach.

NW-SE yellow is rule 290, restricting.  Proceed at Restricted Speed until the entire train has cleared all interlocking and spring switches (if signal is an interlocking or CP signal) and the leading wheels have 1.  Passed a more favorable signal or 2.  Entered non-signaled DCS territory.

If this is a territory where the train is going off onto subsidiary tracks, then it is probably option #2 of restricting.  The train is leaving block signaled territory and entering territory without block signals.  Restricting is a speed which will permits stopping within half the range of vision of a stop signal or restriction, not to exceed 20 mph.