Establishes a spacing (safety) block between two signals using a third as a trip. Signals need not be in
direct succession on the track, with some creative assignments you can create 'zones of control' for following or
passing trains. You should, however, ensure that the block is released at some point (when a train passes the 'trip')
or else the waiting trains will not be able to move past the start of the block if the restriction is active.
You will only be able to select signals which are unassigned *and* capable of displaying a STOP aspect.
Multiple copies of the rule may be added as needed to place safety zones around busy areas such as yards and stations.
Features interactive HTML interface showing signal aspects and forward junction names for each signal.