All You Need to Know About Horns
You will find most of the diesel or petrol driven vehicles come with a device which can make loud mechanical sound which is used to warn the other vehicles running on the way or the passers by.
In fact a train while running on the tracks, sometimes need to make a sound to alert the people crossing the railway tracks or the cattle who often roam around and do not really bother to look whether a train is coming on the same tracks or not.