Ok I'll keep posting here since I don't have an account on trainsim.com. I think I understand now where my confusion is coming from. I was taking the 4 semaphore gantry in the picture above to mean only a train on the 4th (rightmost) track had the clear signal and that my train, being on the third from left, had a danger signal.
But I wasn't taking into consideration that signal poles (always?) appear to the left of the track they are relevant to. Given that, I now believe that the signal in the picture is telling me that the route I'm on is diverging to the right (the 4th track) and, given the height of the 3rd and 4th semaphores are identical, the speed limit is the same as my current one.
Which leads me to another question (sorry!). The picture below shows what I'm calling, until told otherwise, a pair of merging signals. They seem backwards... why do the semaphores not correspond to the tracks? I.e. the leftmost semaphore is mounted on the taller pole which indicates it's the faster line... but the faster line is to the right of the train.