Trevor R (QLD) replied:

I think it refers to the fact that if the amber lights are flashing on this bus then kids are getting on or off this bus and you must slow to 40KPH by law.

bmwrider replied:

You cannot pass a bus with flashing lights at more than 40kph (like a school zone). There is also a sign that shows that you must give way to a bus that indicates that it is reentering the traffic lane.

Garry