Caught on Camera - NORAC's Missing Signal Aspect

If you are looking at older versions of the NORAC signal aspect chart you might notice something a bit odd. Most of the common signals indication have a dwarf option for situations with restricted clearance like tunnels or terminal areas. Because of the understandable choice to limit dwarf signals to 1 or 2 elements, some uncommon aspects like R/Y/G Medium Approach Medium are omitted, however until 2018 NORAC also omitted a far more popular signal, Rule 285 "Approach". For those of you who have been living in a cave, Approach, also known as "Caution" in the UK, is "the yellow light" in railroad signaling. A signal so basic that it appears in elementary school books on how trains work. How Rule 285 was neglected in dwarf form is an interesting story of path dependence. 

The story begins with the lamp color yellow performing double duty as for the Restricting indication. When shown alone on a dwarf signal, yellow Restricting, not Approach, so Approach has to be something else. Well, we have two lamps so why not make Approach Y/R? Well dwarf signals are most often used in terminals, terminals are slow so dwarfs really need a Slow Approach indication.  Single lamp *Y* flashing yellow exists and is the preferred option, but back in the day flashing relays were expensive and unreliable so we should probably have a fixed version of Slow Approach. This is where the fateful choice was made. R/Y Slow Approach could have worked. If the Red lamps burns out the signal becomes a Restricting, but the rules boffins likely didn't want R/Y Restricting on a high signal to be confused with R/Y Slow Approach on a dwarf signal because that mistake would likely result in an accident. Therefore dwarf R/Y was given to Restricting, Y/R was given to Slow Approach and Rule 285 Approach was out of luck.

Slow Approach on Track 1 east at CP-97 instead of Approach.

For the sake of correctness NORAC did offer Rule 285 Approach in the form of a PRR pedestal or a B&O dwarf CPL, but these were never options in color light territory or after position light signals began to be phased out. So what was a railroad to do when it needed Rule 285 in a restricted clearance situation? First option was to use Slow Approach, one loses 15mph within interlocking limits, but outside of interlocking limits the rule becomes "regular" approach with a Medium speed limit. The second option was to use Y/*R* Medium Approach, this bumps the speed passing the signal up from Slow to Medium, but ultimately suffers from the same drawback as Slow Approach in that trains can't come at either of these substitutes on a Clear, trains have to hit an Approach Medium or an Approach Slow first. From my field observations Medium Approach was the preferred alternative and could be displayed on either a 2 or 3 lamp modular stack by lighting the yellow lamp and flashing the red below it.

To be fair, the Seaboard system used by CSX also exhibits this problem despite using only using lunar for Restricting with dwarf Y/R for Slow Approach and R/Y for Medium Approach. By forgoing a flashing medium approach CSX lost its latitude for an "easy" dwarf approach aspect. However it was ultimately NORAC that cracked first and in 2018 they adopted *Y*/R as the dwarf option for "straight" Rule 285 Approach. While this now leaves Rule 282a Advance Approach out in the cold, Approach Medium is pretty much a lossless substitute. Of course these sorts of changes can take some time to filter down and it was only recently where I managed to catch one in the wild at SEPTA's WAYNE JCT where a dwarf has replaced a high signal at the end of a platform.

With this change the ball lands back in CSX's court. Will they make some basic changes to its system like adopting *Y* Advance Approach in addition to *Y*/R dwarf Approach?  Or will they keep looking for more "Canadian Combinations".