I have just posted in my other blog a question on hazard sign usage. Some people here use it to indicate that they want to go straight. The logic is something along this line; if you want to turn left, give a left turn signal; if you want to turn right, give a turn right signal; if you want to go straight? ... turn left and right at the same time. Turn the hazard lamp on! Wow???
No, I am not joking.
After asking around, some people think that this is a correct behavior. That's what they were taught by their friends and family. They never bother reading what's the correct usage. (Hey, is there such manual?)
So, be careful when driving in Indonesia.