In Dublin, Ireland, bus riders would be expected to extend an arm to indicate that they want the bus to stop for them.
When I first traveled to Mexico, I wanted to take the public bus and I tried to find a bus stop or a bus stop pole but I never found one. Then I noticed that whenever someone wanted to hop in the bus, they would have to extend their arm and get the drivers attention. For me, that was very weird that I had to get the drivers attention, but I had to get used to it.