Sometimes during switching duties, a shunting signal would show red, and I have to request permission to pass signal at danger. Than the dispatcher would give me the permission and I would continue with my work. I've noticed this on wsr, but I'm pretty sure it happens in other routes too. So my question is, why didn't he just use that shunting signal to let me know I'm cleared to pass in the first place, instead of requiring me to call and ask for permission? What is the point of shunting signal then?
The signal can’t show anything else but red, because of the cars on the track that you will be coupling to. You have to contact the dispatcher to make sure it is safe to pass the red signal.
The shunting signal is used in ‘normal’ circumstances i.e if you are shunting your stock to a siding for example. Which is a normal, booked move. The reason for getting permission is because it only happens on very rare occasions. One example would be if there is signalling problems then you would have to contact the signaller and ask for their permission to go past the red signal providing all the points/route has been cleared and is safe to proceed first. You should NEVER go past a red signal without permission or a shunt signal being displayed otherwise you will cause a SPAD to yourself and potentially danger other trains in the area.