The big red bus is a government bus. The white buses behind it could be either government buses or privately-owned buses.
Both the government and the private buses run on the same routes. The private buses tend to go as fast as they can on their route to earn as much money as they can. Going as fast as they can generally means they pass other vehicles regardless of how safe or not it is.
Because driving in Sri Lanka generally also means whoever’s the biggest wins.
And if that also means that the buses pull over another 50 meters down the road to pick up new passengers, blocking the road so no other vehicles can get through, or pulling over enough to let the vehicles the bus just passed pass the bus, only for the bus to pass those vehicles again in another kilometer…
And the guy in the brown uniform? That’s a police officer. 🙂