Indonesia [especially Java] has a totally different set of rules- lorries and mopeds don't hold up the faster cars, motorbikes and vans, they just pull out into the oncoming lane to pass or undertake-whichever gives them more space. Oncoming cars then pull to the side to let overtaking cars through. Everyone blips their horn to let people know they are there or about to pass so the obstacle eases to one side or the other to make space.
Once you've been there a few days it all seems totally sensible and works. A three lane motorway with hard shoulder becomes 5 lines of traffic with mopeds and bikes using the six available spaces between the queues to get through.
Mind you, the average speed is far lower than here, journeys take forever as roads are full of potholes and there's no priority given anywhere, so stopping at every junction or turning has to be anticipated.