The common trend among people I noticed that if it's a BIG vehicle out there in left lane and another BIG vehicle guy wants to overtake, if the first one won't budge even after flashing the beam, the later gently moves to right lane and goes without any complaints; on the other hand if it's a Small cab they try to do things that can eventually lead to an accident purposely.

Is there any law stating that the left lane vehicle speed should be within this limit or is it just a courtesy!

Just curious!