Signal Change

[blhanel]

jeffhergert

PTC will light up our approach lit signals for six miles ahead of the train. 

Jeff     

 

And my grandson and I really appreciate that fact... 

[jeffhergert]

PTC will light up our approach lit signals for six miles ahead of the train. 

Jeff     

[PJS1]

BaltACD,

Thanks for your thorough and helpful explanation.  

[BaltACD]

Some territories have 'constant lit' signals, other territories have 'approach lit' signals.  Approach lit signals will turn on when a train enters the track segment in advance of the signal.  The signal will display the condition of the next 2 or 3 track segments beyond the signal.

When a train occupys the track segment beyond the signal - the signal will display its most restrictive indication.  When a train is occupying the 2nd track segment beyond the signal it will display some form of a Approach indication (be prepared to stop at the next signal).  When a train is occupying the 3rd track segment beyond the signal, depending on the signal system being used it will display Clear or Advance Approach (proceed at maximum authorized speed prepared to comply with Approach indication at next signal).

With Approach Lit signals, when the train that lit the signal passes out of that track segment - the signal will extinguish.  With constant lit signals, the signal will display a Red indication as long as the track segment beyond the signal; it will display some form of a Yellow indication when the train clears the track segment beyond the signal, it will display a Green indication when the train clears the 2nd track segment beyond the signal.

The Signal System on the railroad you are viewing may be different.  This discussion DOES NOT interject how signals operate at or in approach to Control Points, where the control operator controls the lining of routes and signals.

Track segments are the distance between 'Intermediate' signals.  The placement of Intermediate signals is a function of the speeds and train sizes that operate on a given territory and are predicated on service braking conditions of a maximum size train operating at maximium authorized speed.  At one time intermediate signals were approximately a mile apart.  During the 80's & 90's that was changed to approximately 2 miles apart.  In the present day that spacing is being changed to approximately 3 miles apart.

[PJS1]

I do most of my train watching along single track railroads in central and south Texas.  

When a train passes a green signal, it turns red.  Assuming there are no other trains on the route at the time, in either direction, how long does the signal stay red before it turns off?   

Also, how far in advance of an oncoming train does the signal switch on?