NEW DELHI — In India, when driving, you basically need a ring of eyeballs around your head to see what’s coming.

Three-wheeled rickshaws whirl out of the roundabouts straight at you, packs of stray dogs dash into the road, huge buses lurch up from behind. And on every side is a thickening stew of bicycle rickshaws, little taxis, fat Mercedes, Uber drivers riveted to their screens, drivers drifting in and out of lanes, and Mario Andretti types hurtling down the main drag six inches from each other.

In this world, the car horn is a survival tool, and a weapon. People use them constantly — to berate, to warn, and especially to get sluggish drivers to move.