James Parker, Vaucluse. When the lights are at orange or red, this flashing light would be on, alerting motorists. It could be on a timer so that it only operated during school hours. Douglas Cliff, Elanora Heights. I tend to use -ise myself, but don't really care much either way.
Some writers are clearly quite uncertain about it, interchanging the two words arbitrarily.
David Green, Turramurra. This opens up the Pandora's box of phonetic spelling. English spelling must remain fixed for many reasons, not least among them enabling us to read what people of different accents and from different times have to say. Brian Kay, Bathurst. Don Moran, Chain Valley Bay.