Etiquette on Road

In this video, blinking emergency lamp (Blinking both side of turning lamp for 2~3 times) means "Thanks" in Korea. It is not warning.

Generally the emergency signal light means "I have trouble" but depend on situation and pre-context of road status, it can be translated into a variety of meanings.

1. "My car is in trouble" : IF car is parked on road shoulder and bonnet hood is opened, it demonstrate car is in trouble and waiting for a help. It is really important to avoid a clash with other cars in dark night. If the car is just parked on road shoulder, it may means "Sorry, I just parked here for temporary". Natural may call him/her.

2. "I'm in hurry": Blinking emergency lamp and go faster and takes every space between cars to go forward. You might run like an ambulance. If your wife start to delivery new baby, you can use this trick. But you can't be exempted from speed ticket.

3. "Excuse me": break in the lane of right(or left) turning from the other lane.
Driver may be a stranger in town or just want to save some time. It means also "I'm sorry but I'm in hurry"

4. "Thanks" : Short 2~3 times of blinking. You can show your gratitude to people who behind you.

5. "I'm in parade" : Sometimes car Hobbyist club members make a parade in the road. Their cars are blinking together and make a formation in the middle of road. Generally it is illegal in Korea but if it is official parade, it can be special exception.

6. "Speed down!" : In highway, if you have to slow down rapidly, this signal may emphasis "Slow down" with break-light. It may be useful to avoid collision from behind. It is useful when the road is in a dense fog.

SO WHAT?
Communication between cars has some variety but is based on old technology and regional & cultural tradition.
For example, short high-beam headlight changing is offensive gesture for car that runs in front of you but it may be showing gratitude in some countries.

Can we develop more sophisticated way of signal using digital technology?
In future, cars on same road may be able to talk each other and share road information and driver's intention. For instance, if your car send emergency signal through radio, all cars which run behind you including cars can't see you from distance can be slow down together as well.

REFERENCE
Half bakery
Yahoo Korea Driver Tip
Donga-ilbo article about safe drive
How signal lamps works