AdvancedApproach
Well-known member
Why on type 4 signals is advance approach a flashing yellow light but on type 6 structures they have two solid yellows?
Advance Approach Display
- Thread starter AdvancedApproach
- Start date
Great question — this touches on the nuanced differences in signal hardware and aspect philosophy across railroad systems.
Advance Approach on Type 4 vs Type 6 Signals
Why the Difference?Railroads in North America often operate with non-unified signal standards, meaning each railroad — or even each subdivision — may define aspects differently based on:
Advance Approach on Type 4 vs Type 6 Signals- Type 4 Signals (Flashing Yellow for Advance Approach):
- These are typically single-head signals using speed signaling logic.
- A flashing yellow indicates "Advance Approach," meaning the next signal is expected to be Approach (solid yellow), and the one after that may be Stop.
- The flashing aspect helps crews anticipate a need to reduce speed further ahead, especially for heavy or fast trains that require longer braking distances.
- Type 6 Signals (Two Solid Yellows for Advance Approach):
- These are often multi-head signals or modular LED-based structures that support more complex aspect combinations.
- Two solid yellows (one over the other) can also indicate "Advance Approach" depending on the railroad’s signal rules — especially in systems using route signaling or hybrid logic.
- The use of two solid yellows instead of flashing may be due to:
- Hardware limitations or preferences (e.g., LED signals may not flash reliably or uniformly).
- Visibility and clarity in certain environments (e.g., tunnels, high-speed corridors).
- Standardization within a subdivision or railroad that prefers solid aspects for consistency.
Why the Difference?Railroads in North America often operate with non-unified signal standards, meaning each railroad — or even each subdivision — may define aspects differently based on:- Historical practices
- Signal hardware (searchlight vs LED vs modular)
- Operational needs (freight vs passenger, speed vs route signaling)
- Safety philosophy and braking distance requirements
Probably no good reason, as (for example) BNSF uses both (but calls it Approach Medium).
CCOR calls flashing yellow Advance Approach, and yellow over yellow Approach Diverging.
CROR calls flashing yellow Advance Clear to Stop, yellow over yellow Clear to Slow (or with a DV plate Clear to Diverging).
Here is a guide explaining some of the logic behind North American signals.
CCOR calls flashing yellow Advance Approach, and yellow over yellow Approach Diverging.
CROR calls flashing yellow Advance Clear to Stop, yellow over yellow Clear to Slow (or with a DV plate Clear to Diverging).
Here is a guide explaining some of the logic behind North American signals.
This should be a Type 5 Type 4 signals are Absolute (stop-go) signals.
From Copilot, stating what you said above, and here's the result:
You're both touching on valid points, and the confusion likely stems from how signal types are classified differently across railroads. Here's a breakdown based on current understanding from North American signaling systems:
There’s no universal standard for signal type numbering across North American railroads. Each railroad may define its own signal types and aspects — even the same aspect (like flashing yellow) might mean different things depending on the system. For example:
Your original description of flashing yellow as Advance Approach is accurate in many speed signaling systems. However, your colleague may be referencing a different classification where Type 4 is reserved for absolute signals, and Advance Approach falls under Type 5. Both views can be correct depending on the railroad’s specific signal rules.
You're both touching on valid points, and the confusion likely stems from how signal types are classified differently across railroads. Here's a breakdown based on current understanding from North American signaling systems:
Signal Type Clarification
- Type 4 Signals (as described earlier):
- Often refer to speed signaling systems.
- A flashing yellow aspect typically means Advance Approach — warning that the next signal is likely Approach (solid yellow), and possibly Stop after that.
- These are not absolute stop signals, but rather intermediate signals that help crews anticipate braking needs.
- Common in systems like CSX, Amtrak, and other speed-signaling railroads.
- Type 5 Signals:
- In some systems, Type 5 may indicate Advance Approach or more complex speed indications.
- These may use multi-head signals or include route signaling elements.
- Your colleague may be referencing a classification where Type 4 is reserved for absolute signals (e.g., Stop/Proceed only), and Type 5 includes more nuanced speed indications like flashing yellow.
Why the Discrepancy?
There’s no universal standard for signal type numbering across North American railroads. Each railroad may define its own signal types and aspects — even the same aspect (like flashing yellow) might mean different things depending on the system. For example:- CSX uses speed signaling where flashing yellow is Advance Approach.
- Union Pacific and BNSF use speed-enhanced route signaling, which may interpret flashing yellow differently.
Summary
Your original description of flashing yellow as Advance Approach is accurate in many speed signaling systems. However, your colleague may be referencing a different classification where Type 4 is reserved for absolute signals, and Advance Approach falls under Type 5. Both views can be correct depending on the railroad’s specific signal rules.AdvancedApproach
Well-known member
Here's what I mean:
While the real world uses similar naming, it differs for us in Trainz. A type 04 signal in Trainz is an Absolute signal and not a permissive or Advance signal, which is Type 05. A type 06d, by Jointed Rail, is the Advance Approach signal.From Copilot, stating what you said above, and here's the result:
You're both touching on valid points, and the confusion likely stems from how signal types are classified differently across railroads. Here's a breakdown based on current understanding from North American signaling systems:
- Type 4 Signals (as described earlier):
- Often refer to speed signaling systems.
- A flashing yellow aspect typically means Advance Approach — warning that the next signal is likely Approach (solid yellow), and possibly Stop after that.
- These are not absolute stop signals, but rather intermediate signals that help crews anticipate braking needs.
- Common in systems like CSX, Amtrak, and other speed-signaling railroads.
- Type 5 Signals:
- In some systems, Type 5 may indicate Advance Approach or more complex speed indications.
- These may use multi-head signals or include route signaling elements.
- Your colleague may be referencing a classification where Type 4 is reserved for absolute signals (e.g., Stop/Proceed only), and Type 5 includes more nuanced speed indications like flashing yellow.
There’s no universal standard for signal type numbering across North American railroads. Each railroad may define its own signal types and aspects — even the same aspect (like flashing yellow) might mean different things depending on the system. For example:
- CSX uses speed signaling where flashing yellow is Advance Approach.
- Union Pacific and BNSF use speed-enhanced route signaling, which may interpret flashing yellow differently.
Your original description of flashing yellow as Advance Approach is accurate in many speed signaling systems. However, your colleague may be referencing a different classification where Type 4 is reserved for absolute signals, and Advance Approach falls under Type 5. Both views can be correct depending on the railroad’s specific signal rules.
AdvancedApproach
Well-known member
An absolute signal can display an advance approach signal which would tell the train crew be prepared to stop short of the second signal.
I've never seen JR's do that.
You bet... NORAC signals between Royal Jct. (Maine) and Rigby (S. Portland, ME), routinely get Advanced Approach signals through multiple interlockings (which are absolute signals).
However.... Trainz signals are... Trainz.
AdvancedApproach
Well-known member
I just posted a picture of a type 4 absolute signal from Jointed Rail doing that. What their smart signals does is give users the option to disable or enable that feature.
AdvancedApproach
Well-known member
Case in point:
Thanks. I'll have to see if they do that because I've never seen it before.
norfolksouthern37
what's a normal map?
The answer to that first question is that some rulesets allow for it, that is all.
The numbers of the signal types is completely made up and was just based on what was already kind of set in Trainz years ago. In a way I regret this, but it is what it is.
05 permissive signals can still display an advanced aspect, the only difference with them is that red is "STOP then Proceed" Rather than "STOP".
06d signal should be the signal immediately preceding a 06 or 08 signal.
The typical setup is still:
06 signals will allow you to choose which version of advance approach to display:
once you click "show advanced approach" this additional option is visible.
The numbers of the signal types is completely made up and was just based on what was already kind of set in Trainz years ago. In a way I regret this, but it is what it is.
05 permissive signals can still display an advanced aspect, the only difference with them is that red is "STOP then Proceed" Rather than "STOP".
06d signal should be the signal immediately preceding a 06 or 08 signal.
The typical setup is still:
06 signals will allow you to choose which version of advance approach to display:
once you click "show advanced approach" this additional option is visible.