Train signal stopping distance to signal

[vader225]

To who ever,  I would like to know what determines to stopping distance a train must stop before the signal? I live 40 feet from CXS's trenton sub there is a main track with a parallel siding. There are signals at both ends. Trains will stop for the red signal but stop there trains at different distances from the signals.

Can someone explane why? 

  Thank You Dennis.

[tree68]

While railroad signals are sort of like highway traffic signals, there is no "cross traffic" or "right turn on red" with which to be concerned - the stop signal on the railroad simply means 'do not pass this point.'  It really doesn't matter exactly where the train is stopped, as long as it doesn't pass the signal in question (there are variations on that, but they don't figure into the basic question).

You could do the same thing at a traffic light, but stopping 100 feet short of the intersection until the light turns green is likely to cause your fellow drivers to be upset with you...

Probably the best answer to your question involves train handling - at what point can the engineer stop his train in a safe and efficient manner?  Sometimes the train can be crept right up to the signal, sometimes it settles in a little earlier.  As long as the train doesn't pass the signal, all is good.

A factor that could figure in is the possibility of blocked crossings.  It may be necessary for a train of a given length to stop closer to the signal to avoid blocking a crossing, while a shorter train has more leeway.

[edblysard]

By different distances do you mean a like away or a ½ mile, or are you talking a few car lengths difference?

The first may be because the rest of the train may block a crossing if they stop closer, the second is because that just where they decided to stop.

[Anonymous]

The simplest explanation is that a freight train's air brake system is slow to respond, and cannot be partially released. You can only make a full release and reapply, which takes time. If the train fits easily in the siding, there's no reason to pull all the way up to the signal.

If you're noticing a pattern with consistent distances for each signal, but trains stop close to one signal and further from another, they could be avoiding activation of a nearby railroad crossing. Many are controlled by the train entering a track circuit, the ends of which are marked yellow joint bars, yellow stripes on the rail, or signs reading "CC" or "XC".

[henry6]

The only regulation is that a train, unless otherwise authorized, cannot pass a stop signal. If switches in and out of a siding or route are thrown by hand, the engineer will stop as soon as his train is clear of the switch or at the clearing point (not fouling adjacent track)to allow his rear man to reboard the train with as little walking as possible. Same at front, stop knowing train is not fouling other tracks and walking distance in minimal to the switch. Then there is "control point 'McD' or 'BK' or 'Chow'" which may be placed somewhere along the track within the train length so stop is to allow the Gofor not to have to walk too far with dinner or lunch. I am sure many engineers and train crews have other "reasons" to stop where they stop, too.

[petitnj]

If the signal is to exit a siding, the trains tend to  get as close as comfortable to the signal. Again engineers will know how responsive the train's brakes are and use that knowledge to judge distances. If it is a CTC signal on a main line the engineers tend to stop anywhere they can see the next signal. On the Jackson Street hill approaching Westminister in St. Paul, MN, the east bound grade is very steep and it is far better to stop the train well back from the CTC signal at mile post 2. 

[Deggesty]

Once in a great while, you may find a situation like I one that I witnessed last month when going to Los Angeles from Fort Worth--a double meet at one pass track; two eastbound freights and a westbound passenger train. One EB held the main, but it had to stop far enough short as to allow the WB to also occupy the main until the other EB (which was empty [as far as I could tell] autoracks). Our conductor had to keep telling our engineer that we were not clear of the fouling point; apparently the EB train on the main had not allowed enough distance for us to clear, but we were in the clear before the second EB arrived; after he was gone, we backed out to where we could proceed on the pass track. You can be sure that our engineer had specific instructions which made it possible for the maneuver to be performed.

[jeffhergert]

Technical reasons aside, they stop at different places because you have different engineers, each with different abilities and different philosophies on how trains are handled.  Some guys like to charge up to a signal or other stopping point while others come up slow and cautious.  Some will get as close to a signal as they can, others have a "good enough" attitude.  (We're in the clear and can see the next signal, good enough.)  

Most rule books also have a requirement to stop a certain distance from a stop signal, especially when the signal governs movement over a switch, when train length permits.  For us it's 400 ft.  You can be farther away, but they don't want you closer unless train length requires it.

If there isn't an access road running along the track, there probably is one to the signal installation.  The farther back a train stops the farther the managers have to walk to board the train when they want to make a surprise visit. 

Jeff