On a multi-lane highway, freeway or expressway, it is essential to stay on the right e as often as possible.
Stay on the right for your safety
It is a habit or resume, which allows traffic flow and avoid stress of too brutal . When you pass a vehicle on the highway, do not forget to fall back on the right track, once the passing is achieved. The left lane is then free for other vehicles to pass you.
There are still motorists who take the highway for a F1 circuit and arriving at full speed behind you. Needless to prevent them from going to cause you to hit. For them the stress of the road, for you the zen way of driving.