how is the trigger enivorment work? 
 
is it just random? anyone drive pass the triggerable and they just press a button and it trigger?
 
what im trying to say is there skill involve in the triggering of enviorment? or anyone pass by and do it?

You have to fill up the meter a certain amount (one bar for most things, three for specials), and then push a button to trigger it.  
 
Nothing happens randomly, aside from the AI drivers. I'm pretty sure that you could play an entire race and have nothing explode (but it would have to be all non-AI players).  
 
Yes, there is some skill in using the environment, but a lot of it is simply just a matter of memorizing where the triggers are. But on the other hand, you need to have filled the meter in the first place...

how to fill the meter? what we have to do? drift? ram other cars? 

drift draft

i see. so trigger enviorment is like taking place of nitrous. they should have nitrous though.
 
and why some games use draft as rewarding? is draft even real in reality? do science have draft? in reality a car go behind other car and make it go faster? i dont like this draft thing on games. drifting and air tricks to fill up boost is good though. never understand draft. not trolling. really dont understand draft.

" and why some games use draft as rewarding? is draft even real in reality? do science have draft? in reality a car go behind other car and make it go faster? i dont like this draft thing on games. drifting and air tricks to fill up boost is good though. never understand draft. not trolling. really dont understand draft. "

" @AnnouncerGXZ said:

" and why some games use draft as rewarding? is draft even real in reality? do science have draft? in reality a car go behind other car and make it go faster? i dont like this draft thing on games. drifting and air tricks to fill up boost is good though. never understand draft. not trolling. really dont understand draft. "

Um, yes. Drafting is a very real thing, and can play a major part in racing. That's why it's used in many racing games.
 
Wikipedia has more information on drafting here. "