i've driven the North-South highway back to Penang before. let me tell you, the drive can be tiring when things get monotonous. falling into the state of semi consciousness is a sure thing. falling asleep is a different story all together.
normally, when you are in a state of semi consciousness and you don't do something about it, sleep will take over. and when this happens, everything around you is in danger and so are you.
how i beat falling into semi consciousness while driving a long and monotonous drive is to vary my speed. when i'm speeding, my mind tends to be more alert and my reaction to events are sharper. but of course, i speed with responsibility lah.
and when i'm fully charged up, i'll slow down and take in the greens around me.