according to the comment section, this is ineffective as all hell as literally nobody seems to know about it - ergo no one would recognize it as a sign to back away, defeating the purpose, yay,(reply>), I'd assume it was some kind of spraying, digging or hydraulic machine or gears grinding.  Not a vehicle reversing.,(reply>), Everyone entering the site, even visitors, would be required to have site-specific safety training (or be <b>very</b> closely supervised), so they'd know.,(reply>), @thelonelysnowelf (孤独な雪の妖精) what else can i say but... No?,(reply>), Anyone who doesn't at least look in the direction of this noise <b>deserves</b> to be run over. <b>Twice.</b>,(reply>), When did you go through trainining to recognise what the beeping sound meant.