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?