5.1. ABSOLUTE SIGNAL BLOCKING

 Absolute Signal Blocking (ASB) is implemented by the Train Controller.
 ASB is used to protect Workers who occupy a defined Section of Track for work in
the Danger Zone while Rail Traffic is not Authorised to enter the Section.
 The PO and the Train Controller record the use of ASB for Protection.
 The PO receives confirmation of ASB on the Absolute Signal Blocking Form.