In Altstetten control center, view provided by system for train speed optimization

North is roughly down; Zurich is to the left and the lines to Lenzburg and Baden are to the right

If the system detects that a train coming from Lenzburg will have to stop or slow down for a train from Baden that is preceding it on the express track to Zurich, the system uses the lineside signals to slow down the Lenzburg train earlier than required for safety so it can accellerate again faster once the Baden train is far enough ahead.