I recently rented a car in Jeju, South Korea. While I managed to get used to most of the traffic rules there which are different from what I'm used to (such as right turn on a red light) I got really confused by some traffic lights. Several times I observed the following sequence:
Red > Green > Amber and Green > Green > Amber > Red
The Amber and Green part is only on for a second or so before going back to Green only.
Now the bold part has me confused for two reasons:
- I'm used to Amber and Red together (before changing to red), but I've never seen Amber and Green together. I thought it could mean that it's about to change to Red, but that's obviously not what's happening since it goes back to Green.
- I would think that Amber usually indicates a change of the signal, however here it went right back to Green.
So what does this mean?
I found animations online where the same thing happens, but with a green arrow. (See for instance this Korean wikipedia article). This is not what I saw, there was no green arrow. My best guess is that this happens when one of the other traffic lights on the intersection go through a change and this is just to indicate that change.