the trouble is now rather than hearing a beep and knowing that something is happening, it just sounds like the truck is struggling to tune into the radio so you don't think it might be reversing,(reply>), gteaz was it fatal?,(reply>), I got ran over by a forklift truck whilst standing next the industrial paper shredder.,(reply>), You don't care if it's reversing. You care that it's coming towards you or not, which you can hear. It's for reversing because the driver is less likely to react to you, but you can react to the driver. When going forward, it's up to the driver to avoid you. Or we could just have trucks spew noise all the time...,(reply>), ​@Mr. W More importantly, if that hiss is 2.5 meters to your back left when you're on a construction site, you'll immediately realise some piece of machinery is suddenly very close to you making a repeating noise. If it's getting closer and closer you'll quickly be alerted too.<br>Everyone else further away (e.g. public outside the construction site) hears it and can safely ignore it as some sound far enough away to not be alerting.<br>The great thing about this is that the alarming effect is proportionate to the closeness to the vehicle and as such proportionate to the danger of being run over..<br><br><br>This also explains why people that are never close to these trucks have a harder time imagining the sound as alarming. ;-)on a construction site,(reply>), It’s more about our ears recognizing the direction of the sound rather than recognizing its meaning. The point is the hiss grabs your attention and you know exactly which direction it’s coming from. Lots of other sounds might put you on alert but it’s harder for our ears to pick out their source when there are lots of trucks around.