As extracted from the US department of state's website:
On traffic in India:
On Indian roads, the safest driving policy is to always assume that other drivers will not respond to a traffic situation in the same way you would in the United States. On Indian roads, might makes right, and buses and trucks epitomize this fact. For instance, buses and trucks often run red lights and merge directly into traffic at yield points and traffic circles. Cars, auto-rickshaws, bicycles and pedestrians behave only slightly more cautiously. Frequent use of one's horn or flashing of headlights to announce one's presence is both customary and wise.
On the few divided highways one can expect to meet local transportation traveling in the wrong direction, often without lights. Heavy traffic is the norm and includes (but is not limited to) overloaded trucks and buses, scooters, pedestrians, bullock and camel carts, horse or elephant riders en route to weddings, bicycles, and free-roaming livestock. Traffic in India moves on the left. It is important to be alert while crossing streets and intersections, especially after dark as traffic is coming in the "wrong" direction (i.e., from the left).
If a driver hits a pedestrian or a cow, the vehicle and its occupants are at risk of being attacked by passersby.
