Dear BMW driver, why turn on hazard lights after colliding with bus when you could have used signal lights to prevent crash?

Signalling your intention to change lanes with the use of the turn signal lights should be the norm for all drivers.

You would think that is obvious, but clearly this BMW driver thought otherwise.

In a clip posted on Beh Chia Lor - Singapore Road by Eric Ng, the BMW driver can be seen travelling near Stadium Road.

However, he then attempts to change lanes without using the signal lights.

A bus driver who is changing lanes, after indicating that with his signal light, ends up knocking the BMW.

At this point, the BMW driver turns on his hazard lights to indicate that he has gotten into an accident.

Which begs the question, if your hazard lights are working, surely you could have used the signal lights?

Why would you rather use the hazard lights after the crash, rather than using the signal lights to prevent the accident in the first place?