Expanding on what I said earlier, I was taught to have the lights on way before an engine start (approx. 5 mins) (rotating beacon, nav lights..). This allowed fellow aircrew a visual warning of live engines. (even if not running) Also, ground staff had to be aware the engines were live while lights were flashing. (but engines are off)
However, this didn't allow for Joe Public as they didn't know about the lights.
Nowadays, Joe Public can't venture onto an airfield without an ASIC escort,.. so with the appropriate ASIC escort there should be no randoms on an airfield??
But we all know Joe Public does end up on the field and hence the warning.... a bit old school considering... I am not saying it is wrong but I have never seen anyone near me during a start....