Almost every vehicle on the highways of India apart from passenger cars has some version of a sign telling you to blow your horn. One of my drivers explained that if you don't have side mirrors you want someone who is trying to pass you to use the horn to give you a warning.
But lots of the large trucks have mirrors and the signs, and carts with horses and camels and no mirrors at all do as well. And the signs are always colorful and often really elaborate, like this one (although I'm not sure what kind of animal that's supposed to be -- it looks like a cow, but that long neck is more like a camel: a cowmel?)
There are also tassels and ribbons and bells hanging from the sides and backs of carts and trucks. The decoration is a way of celebrating the act of working, by making everything about it as beautiful as possible.