Signal Error? Getting A "approach Medium" When It Should Be An "advance Approach"

I don't know for sure if this is the case with CSX so maybe I'm wrong here, but I'm pretty sure that the signal before an "Approach" (Yellow, Yellow over Red, Yellow over Red over Red) should be an Advance Approach, but in TSW I always get a "Approach Medium" (Yellow over Green or Yellow over Green over Red). Can anyone shed some light on this?

http://signals.jovet.net/rules/CSX Signal Rules.pdf

 

You are right. DTG can’t get anything right.

 

Thanks. Dovetail?

 

Signal progressions can vary.

Advance Approach > Approach > Stop is a common one

There are less common progressions like
Approach Limited > Approach > Stop

Approach Medium > Approach > Stop seems unlikely but may be possible

 

As cActUsjUiCe pointed out, the signals that can be encountered vary. Always remember that the signals are implemented to suit the railroad and its operational traffic, not the other way around. The key component is braking distance. If the fastest or heaviest train cannot physically stop between Approach and Stop, then the train needs earlier warning to slow down. The reason it cannot stop could be the spacing of the signals, or the topography, or the speed limits, or the weight/make-up of the train, or a combination of these. If that still isn't enough warning for the fastest or heaviest train, other warning signals may be invoked. Other locations my require just a little less warning. Keep this in mind:
1. Advance Approach should always mean that the second signal after Advance Approach requires a stop, and that the first signal after Advance Approach displays Approach.
2. Some trains may need to slow down less or more in this situation. Advance Approach does not usually invoke any train handling speed limits, where as something like Approach Medium does force the train to slow down before the subsequent signal.
3. Not all signaling schemas have Advance Approach. For those that do not, signal rules like Approach Medium are ready to fill its place.
4. CSX, in particular, has chosen Yellow over Yellow (over Red) to mean Advance Approach, and given the expense of implementing this signal aspect, using Approach Slow, Approach Medium, or Approach Limited increases safety because of #2. So, it seems CSX has diminished the implementation of Advance Approach.
5. Signal rules along the lines of Advance Approach for changing tracks are not nearly as common (e.g. Medium Advance Approach), but other rules (Medium Approach Slow, Medium Approach Medium) sometimes are, like #3, ready to be used in the same manner.

Edit: Having written all that, I have seen examples of incorrect signaling. A Slow Clear encountered after a Clear, for example. So, it's not my intention to write that the implementation of signals is perfect. I must admit that signaling is usually a neglected topic in train simulation games, as it's very difficult to even understand it well enough in the first place, let alone program it right.