It depends. I don't think it's wise to stick to hard-and-fast rules with regard to the white lines. Generally I ride about 2-3' to the left of the white line, particularly if there is no paved shoulder or the shoulder is littered with rocks and glass. However, if it is a busy road with fast traffic and the shoulder is wide and clean, I will often ride to the right of the white line. Sometimes I do both. I stay to the left, keeping my eye out for traffic in my mirror, and then drift right as the traffic approaches. Personally, I think it is foolish to slavishly "take the lane" on a busy road with fast traffic when there is a wide clean shoulder to the right of the white line, but go for it you have enough confidence in drivers to see you and pass safely.