Got the answer .Thank you all.

[Kelena]

The customary way of addressing a slow driver in front of you is to blink your headlights quickly a couple of times. It may not have the desired affect and is unlikely to get them to pull over enough to allow you to pass, but that's how you are supposed to do it. You don't drive on the shoulder. The shoulder is for emergencies. I am so sad that schools no longer provide driver training.