It is always corteous to YIELD TO THE FASTER VEHICLE. Never mind if he is doing 110kph or 320kph, if you are (or me, in most cases) the slower vehicle, YIELD. Or at least show that you intend to yield at the next possible opportunity. As M54 has stated, impeding traffic is dangerous and is one of the leading causes of expressway pile ups (as it creates an 'artificial' traffic jam). Speeding vehicles, on the other hand, are usually just involved in one-car (themselves) crashes. And we couldn't care less if they rolled their flashy red sportcars into a ball of junk 2kms away.

I don't waste my time flashing other vehicles. I just spend a moment of my time to let them know that they are total menaces on the road.

I remember one of our drivers, a total left lane bandit. Galit na galit dun sa nagfa-flash sa likod niya. Ako pa tuloy ang nahiya. I already saw the vehicle do a corteous flash more than 5 carlengths away from where we were. Pero engot lang siguro talaga yung kasama ko. Ako pa nagsabi na itabi na niya.

Passing on the right (as already posted) is not only ILLEGAL, it is also DANGEROUS. Just because everyone's doing it, ok na siya. Ang problema tuloy, the drivers who do the right thing ang lumalabas pang kontrabida sa daan vs. the uneducated MASA.

That's why I take the time to report these violators (LEFT LANE BANDITS) when I chance upon NLEX HP units.