Amazingly, it turns out that elephants can identify different herds miles away by using their feet to sense their neighbours’ characteristic, low frequency rumblings. These sounds are transmitted through the earth as ‘infrasound’ waves, which are only mildly attentuated in transit and which are too low for humans to hear.
Although these noises aren’t experienced by being heard, people do react to infrasound. It tends to create a strong feeling of fearfulness and awe -often associated with apparently ghostly phenomena.
Today’s invention is to use this psychological reaction to encourage motorists to decrease their speed.
Sections of roadway identified as the approaches to accident blackspots could be coated with textured paint (of very low spatial frequency) so that car tyres rolling along would gradually begin to generate infrasound waves and scare drivers enough to make them slow down.