Had to look up contraflow system, because I've never seen or heard of it?
It may be specific to Birmingham, but you have to know the rules for it to pass your UK driving license test. It's a way of changing which lanes go which way to accommodate the flow of traffic.
Say, if a road has 7 lanes, there's no median. In the morning when everyone's going into the city center, 4 lanes will go that way and 2 lanes will go the other. (With 1 empty in the middle for safety margin).
Then, at night when people drive home, it reverses so 4 lanes go outside the city center while 2 go inside.
Digital signs over the road show you which lanes can drive which way.
It's brilliant, really. Clever way to maximize traffic flow.