There seems to be an awful lot of fluffing around the issue here. The airside driver must have an airside driving permit and vehicle RT certificate.
If he has crossed a holding point (his training would have taught him what this is) then he MUST NOT re-enter the runway without clearance.
It is of no relevance that the tower controller should have foreseen a potential problem (there is no requirement to) and there is also no requirement to report vacated. Having said that if a vehicle is cleared to operate on the runway it is good practice to report vacated but the fact that the tower controller saw him cross the holding point makes it perfectly acceptable to clear an aircraft to takeoff/land.
Grass roots fact is that the driver is at fault (it's a runway incursion). MOR it, accept it and learn from it.
Care to show the material from which you're making these statements? Especially with regards to crossing the holding point = vacated runway? For a crossing, maybe, but for an inspection...you're going to have to show me your evidence on that one I'm afraid.
So, it's fine for the controller not to foresee the potential problem because they weren't required to...but not fine for the driver to re-enter the runway having not called vacated when we've established there's no requirement for that either?
It's only a runway incursion if he enters the runway without permission...but they HAD permission, and in their eyes they hadn't reported vacated, hadn't given the runway back and so had never left the runway. It's not cut and dry and simple. It's a case of two people getting their wires crossed - the controller, for thinking the vehicle had vacated when the vehicle hadn't said so and obviously didn't think they'd vacated. And the vehicle's for crossing the holding point and doing the 180 without keeping ATC informed.