More on Interlocking signals

NW Mailing List nw-mailing-list at
Thu Oct 31 22:16:14 EDT 2013

I have been a lurker here for a little bit and have some questions regarding N&W signals and the conversion from CPL's to standard tri-light safetran signals which has been happening for the last 15-20 years.

First question is in regards to signals at the end of a siding. Most all other railroads when approaching the end of a signaled siding would have a dwarf on the siding track to the main or a regular signal mast which would give a "less favorable" aspect than clear or approach. You would think in N&W signal terms, when approaching the end of a signaled siding to a single main, you would receive a "diverging" aspect of some kind, like diverging clear, or diverging approach. In fact, some signal replacement projects did exactly this. Where some just kept with the "N&W way" of allowing a clear signal at the end of the siding to single main track.

What was the rationale for N&W doing this back in the day

What is the rationale for the way they are doing things now.

-Troy Nolen
Tampa, FLA.

---- NW Mailing List <nw-mailing-list at> wrote:

> Back before ditch lights, some trainmen referred to the Restricting aspect

> as a "ditch light."


> Grant Carpenter


> > Date: Sat, 5 Oct 2013

> >

> > Jim:

> > If I'm deciperhing this diagram correctly, the signal at the entring

> > end of the siding is displaying an APPROACH DIVERGING. The

> > bottom target shows three amber lights pointed toward the main.

> > The center amber light shouldn't be there. Bear in mind that not

> > all sidings were bonded and therefore couldn't detect if the siding

> > was occupied or if there were track defects or a switch not properly

> > line. For non-bonded sidings, the signal at the entering end of the

> > siding would desplay RESTRICTING. On the Pittsburgh Division, the

> > W&LE had a multitude of non-bonded sidings and maximum

> > authorized speed to enter was 15 MPH. N&W's Safety Department

> > ID'ed restricitng signals by noting that the diagonal signal on the

> > bottom target point to the ditch and if you don't comply with the

> > indication, the ditch is exactly where you're going. Harry Bundy



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