Absolute Signal Blocking (ASB) is a method of working in the Danger Zone by
maintaining Controlled Absolute Signals at Stop to exclude Rail Traffic from a Section
of Track.
The ASB method must not be used for work that breaks the Track or affects
Infrastructure integrity.
ASB is issued to a PO and gives Exclusive Occupancy for the agreed period of time.
The ASB method:
must not be used where a Work on Track Authority is in place; and
must be applied to Controlled Absolute Signals only.
ASB may be used:
for work not requiring tools;
for work using equipment which can be removed from the Track by Workers without
mechanical assistance;
at Active Control Level Crossings, or
to allow Vehicles to directly cross the Track.
If ASB is used one Worker may work alone. In this case, that Worker is also the PO.