There are no certainty's when driving:
The green light might suddenly turn red skipping yellow,
The motorcyclist may fall off his bike right in front of you,
The car signalling left may change their mind and turn right,
That pedestrian that is looking right at you might still walk right into traffic,
That car that has been side by side with you on the highway for 2 miles, might suddenly change into your lane.,
The car that starts to go in front of you may stop for no reason at all.
Yes the odds of these things are small, but they do happen. A good driver does not take things for granted. He or she prepares and thinks ahead. They get into habit where they subconsciously leave room, watch for signs of non-normal behavior and always do not trust the other guy.
For example - a good driver approaching a green light thinks "how long has it been green?" and rather than speeding up maintains a steady speed or even slows down depending on how long the light has been green. By not coming to a screeching stop, they make it safer for themselves and the drivers following them.
ChrisZ
