Freight Dog:
Carryfast:
If the worker must know the ‘foreseeable’ ‘duration’ of the ‘period’ of availability’ obviously before starting it.Then logically they’ll need to know exactly when the call to resume work will actually take place before starting the period ?.
I see what you’re getting at. I think you’ve got it a bit too complicated. What they mean is you have to know how long the theoretical time of poa is planned to be. Not when Poa does actually end sooner because a call to work comes. Would be pointless having it if they knew when they’d need you in advance.
Say a known block of 3 hours of poa. If you were called after an hour to work the poa then of course ends and another mode starts, say other work or driving, could even be break. They might say " you don’t have to wait in the driver’s waiting room now, take your lunch, you’re off somewhere at 1pm". It’s how long the planned length of poa is that you have to know before, the 3 hours bit.
We have standby and it’s works exactly the same. It’s to stop you hanging by the phone for indefinite periods so you can plan breaks/shut eye
It isn’t a question of if the ‘planned’ period ends sooner than anticipated.It’s the fact that it’s impossible to establish any supposed set duration of even the supposed ‘planned’ period without first having pre established an anticipated time of being called back to resume work,because it’s only obviously that call which will end the duration of the period.Which as in the description you’ve given totally defeats the object of POA ( standby ) anyway because if you have a reasonable idea of when you’ll be called to resume work then you can just book that as break anyway.While if the call is sooner than anticipated that just means a shorter,or possibly,aborted break regardless.In all cases break will do the job just fine with no need to complicate matters with the silly idea of a period of availability ‘standby’.Which is itself subject to the contradictory condition that the worker must know when the call to resume work will happen anyway.IE it’s anything but standby.
Then put that in the real world of a driver on the 4.5 driving time limit on arrival at a tipping/loading point,then booking POA instead of break,obviously won’t satisfy the rule that only taking break,not POA,will reset the driving time period.In which case what’s the point of POA in that typical situation.Let alone the idea that a driver has wasted 1 hour + of valuable break provision in that regard,during a channel crossing for example,by booking it as POA instead of break.
While as I’ve said it only makes some sense in the case of something like being told that there’s no vehicle available or it’s being loaded/tipped for however long when starting a shift.In which case taking a break immediately when starting a shift would be pointless.But which then defeats the object under the rules when the guvnor says we haven’t got a clue how long you’re going to have to wait or how long it will take.IE that’s clearly POA ( standby ) in that case by any logical definition.But which by the wording of the rules as it stands isn’t actually allowed within that supposed provision because the guvnor hasn’t got the slightest clue how long it’s going to take and when the driver can actually start work. 
While the example which you’ve described just confirms that being on break while at the same time waiting for a call to resume work isn’t mutually exclusive.
However that obviously all changes if we’re discussing POA in the terms of daily rest period when waiting for a call to resume work can’t possibly go together with daily rest.IE 10 hour shift,3 hours POA,11 hours daily rest which is my bet what it’s really there for,to seperate daily rest from standby not break.In which case it’s obvious that the driver would need to know when the standby period ends so they can start their daily rest period. 
