Last night while waiting for the train at South Yarra station in Melbourne, I saw these reflective triangles stuck on the sides of the train track rails. They were evenly spaced a few metres apart for as far as I could see down both ways of the tracks. They could only be seen on the far pair of tracks, and the tracks on the other side of the platform also had these little triangles on the far pair of tracks. I'm assuming that there are also triangles on the near pair, but stuck on the other side of the rails where I couldn't see them.
I can't work out what these reflective triangles might be used for. What is their purpose?