Railroad trackside signal lights

[BaltACD]

Perry Babin

Are the signal lights turned off to extend the lamp life or does it have some other significance?

In the following clip, there are lights on the outsides of the double track. When the train triggers the lights, both sets switch on. The one on the right has an orange light which would mean to go slow. Is this for a train that would be on the right-side track?

https://youtu.be/GVVYFLQESZs?t=60

If so, why would the train on the right-side track have a speed restriction?

The answers here helped me use better search terms which led me to the following site. 

http://www.mikeroque.com/railroad-signals/

There are two methods of for the display of signals - Constant Lit or Approach Lit.

With Constant Lit the signals stay lighted all the time and display whatever signal indication the Automatic Block Signal system demands that it show.

Approach Lit signals only come on when a train activates the track occupancy circuit that approaches the signal, otherwise the signal stays dark.

In territories where signals govern multiple track - those signals will display the required Automatic Block Signal indications for ALL tracks - if the signal system is Approach Lit all the signals will turn on to display the indications when the track circuit approaching the signal location becomes occupied by a train moving in either direction.

In general - there is a progression for the signal indications that get displayed to a train.  In its simplest form the progression is CLEAR, APPROACH, STOP.  A Clear signal indicates that the TWO track segments beyond the signal have no trains or cars on the track.  A Approach signal indicates that the track segment beyond the signal has no train or car, however, the second track segment beyond the Approach signal DOES contain a train or cars.  A Stop or Red signal can have two meanings - if the signal mast contains a number plate (normally the milepost is indicated) it is considered a intermediate signals the signal indication is 'Restricted Proceed' pass the signal at Restricted Speed looking for a train or other obstruction ahead.  If the Red signal does not have a number plate, it is considered an Absolute Signal - to pass the signal the train crew must contact the Train Dispater (or Control Operator) to get specific authority to pass the signal and specific actions they must take in order to pass the signal (line switch positions, leaving switches on or off power).  If the Train Dispatcher cannot be contacted for authority to pass the Absolute Stop signal - the train will stay at that location until they can get such authority or the signal lines and displays an indication that will permit the train to pass the signal.

[Perry Babin]

Are the signal lights turned off to extend the lamp life or does it have some other significance?

In the following clip, there are lights on the outsides of the double track. When the train triggers the lights, both sets switch on. The one on the right has an orange light which would mean to go slow. Is this for a train that would be on the right-side track?

https://youtu.be/GVVYFLQESZs?t=60

If so, why would the train on the right-side track have a speed restriction?

The answers here helped me use better search terms which led me to the following site. 

http://www.mikeroque.com/railroad-signals/

 

[tree68]

As has been noted - each railroad has their own schema.  Sometimes they are at cross purposes - a given indication means one thing on one railroad, and something different on another.  This has led to problems, like the engineer in the Chicago area who applied the wrong rule and ended up rear-ending another train.

But, a few rules of thumb you may find useful.  Red usually means stop.  Amber usually means slow down.  Green means go.  Lunar (light blue) usually carries some special meaning.  The following examples are just that.  

If there are stacked signals, the top signal generally applies to track speed.  Hence the term "high green."

The middle signal refers to medium speed.  A train seeing a green signal in the middle of three heads will be proceeding at medium speed, often through some form of interlocking.

The bottom signal refers to slow speed.  Kind of like the middle head, it's often an indication of some sort of interlocking, like a diverging route.

There are "always" three heads at an interlocking.  If there are only two, the bottom is assumed to be red (any head not displaying another aspect will be red.  Sometimes you'll see three heads of which the top one is always red, because there will never be a track speed indication given.

There are also flashing aspects.  Consult your favorite railroad's rule for explanations.

As I said, though, these are very general "rules" - not something to live or die by.

I should also note that many (most?) signal systems are speed, not route.  The key is understanding a given plant and knowing that such-and-such aspect generally means that a certain action or routing will be involved.

Signal rules tend to be quite intense - get some basics down and you'll know enough to fan knowledgeably.

[rdamon]

A good reference chart source:

https://signals.jovet.net/rules/index.html

[SD70Dude]

You'd have to read the signals section in each individual rulebook.  The U.S. has several, including the GCOR, USOR and NORAC.  Canada only has one (CROR) but each railroad has their own version that differs slightly, for example CP uses some unusual signal indications that are not found in the CN CROR.  

[Perry Babin]

Is there a definitive guide for the signal lights for US railroads? I've found a lot for Canada and Europe but nothing that's consistent for US railroads.