• Advance signals only purpose is to tell you the state of the next main signal. Advance signals can be recognized by their lights being in a diagonal setup /
  
• Main signals are the only light signals indicated in the User Interface HUD. They can be recognized by their rectangular shape.
  
• Advance and main signals can be combined. In that case the advance signal refers to the next main signal. The upper signal is the main singal, the lower signal is the advance signal.
  
• A yellow/green signal indicates a 40km/h speed limit, unless the signal also provided an illuminated number. In that case the speed limit is the indicated number times 10km/h.
  
• The user interface route information HUD only displays line speeds. It does not show speed resctrictions given by signals.

I made a screenshot of a few signals and will explain what they mean and how they work. To do this, I started a Quick Drive on the Hamburg-Lübeck route, starting from Hamburg Hbf to Lübeck. If you start this Quick Drive, you'll run into the same signals in the same order. The train I'm driving is a BR266, but that makes no difference for the signals. I skipped signals that show no new aspect, and only explain where I ran into something new.



When we get spawned at Hamburg Hbf we immediately see this signal. To make stuff complicated right away, the signal has an illuminated "L". Because it's not a number, it says nothing about speed. Illuminated letters are used to indicate where you're going to, which route has been set up. In this case, it shows the "L" of Lübeck.

The main signal has a green/yellow aspect. Without an illuminated number, this means a speed limit of 40km/h.

The advance signal has a green/green aspect, which tells us the next main signal is clear (green).

The "H" Halt sign is where a passenger train would stop to let people board/unboard the train.



This is one of the many mileposts, indicating where you are on the route. They usually come every 200 meters. The upper number is the amount of kilometers, the lower number is in units of 100 meter.

Do not confuse these with speed limit signs, which are square and only have one number.



The main signal is clear, as indicated by the previous advance signal. We can proceed at line speed.

The advance signal warns us that the next main signal gives us a speed restriction. The illuminated "6" tells us that speed restriction is 60km/h. Reduce speed so that the next main signal is not passed at more than 60km/h.



The main signal gives us a 60km/h speed restriction, as indicated by the previous advance signal.

The advance signal here has a different shape. It's rectangular, and not diagonal. However, the lights are still in diagonal position. That's the easiest way to distinguish those signals. Green/green aspect means the next signal is clear.



This sign sets a new line speed for us. Multiply the number times 10. In this case, 100km/h. Since the new line speed is higher than the current line speed, we have not seen an advance sign.



This is probably the most common aspect you'll see on German routes. Main signal is clear, so proceed at line speed.

Advance signal is also clear, so next main signal is clear too. Proceed at line speed.



We've already passed an advance signal, but we're passing another one as we approach the main signal. The white light indicates the distance to the main signal is shorter than usual. The reason we're getting another advance signal (basically a repeater signal), is because our line of sight on the main signal is blocked by the upcoming station. So it's possible for a main signal to have multiple advance signals.

The advance signal at the left applies to the other track, but it's nice to see the differently shaped advance signals giving the same aspect. Note that the lights are always in diagonal setup.



Main signal is clear, proceed at line speed.

Advance signal is clear, so at next signal, proceed at line speed.

New line speed: 120km/h



This is not our signal, but this is now a yellow/yellow advance signal looks like. It indicates the next main signal is red. The white light indicates the distance to the main signal is shorter than usual.



Main signals and advance signals are often, but not always, combined. In this case we only see a main signal.

No advance signal means we don't know what the main signal will give us, yet. We yet have to pass an advance signal.



The striped signs indicate an advance signal is nearing. Note that advance signals are not shows on your user interface route information HUD.



Advance signal is clear, so next main signal can be passed at line speed.



New line speed: 160km/h. Because the new line speed is higher than the current line speed, we have not been given an advance speed limit sign.



These signs indicate that a lower line speed is nearing. Our current line speed is 160km/h, as indicated by the previous sign. The new line speed will be 120km/h. Reduce speed.



This is where the new line speed starts. Do not pass this sign faster than 120km/h.



Main signal is green, proceed at line speed. Line speed currently is 120km/h.

Advance signal is green, proceed at line speed. However, line speed will be reduced to 100km/h.



Arrow signs above other signs indicate that the sign applies to the track the arrow points to.



This is where it gets tricky. The advance signal is giving us a speed restriction of 60km/h. We need to reduce speed and pass the next main signal no faster than 60km/h. The position of the next main signal is shown on the user interface route information HUD. However, the route information HUD only displays line speeds. It does not display any speed restrictions given by signals. So, even though the HUD shows us a 120km/h line speed at the signal, we need to slow down to 60km/h before we pass that signal.

To make things more tricky, the advance signal shows us a small white light. That indicates the distance to the main signal is shorter than usual. Which means we have to act quickly.



Main signal indicates a speed restriction of 60km/h. Note that this speed restriction is not shown on the user interface route information HUD.

Advance signal is clear, which means we can pass the next main signal at line speed. The HUD shows us that line speed will be 60km/h when we pass that next main signal.

New line speed is 120km/h, but we're restricted to 60km/h.

As you can see, I didn't reduce enough speed. I'm approaching the signal at 90km/h. My excuse is that I was too busy taking screenshots of signals ;)