Maybe I should reword it as "special exception". But if the JCG pilot genuinely thought his plane was an exception (having already been allowed to enter the runway further down from the normal taxiway AND being given No.1 for departure) then it is also possible that he could have disregarded the stopbar as well.
Furthermore how would a pilot react is the stopbar was off due to a malfunction, but no ATC clearance had been given? The key thing is that the ATC controls both the stopbar and radio instructions, and following ATC is the only way to avoid this disaster.
Furthermore the stopbars may in fact have been off to allow for planes and vehicles to cross the runway, and turned on only when the plane was about to land. This would also have not stopped the JCG plane from entering the runway. Many vehicles would not have to obtain permission to cross a runway if they operate on it and stopbars are irrelevant for them when turned off.
But generally I agree with the three following safety recommendations:
- Retraining pilots more to emphasize the terminology for entering a runway and takeoff clearance, assuming that there are no exceptions to the terminology.
- Full time monitoring of runway radar for any unwarranted incursions.
- Stopbars in use at all times