Broken white lines between two lanes traveling in the same direction mean:

Broken (dashed) white lines separate two lanes traveling in the same direction. They indicate lane changes are permitted when safe — when there is room, no vehicle in the lane you are moving to, and visibility allows. Solid white lines between two lanes of the same direction discourage but do not necessarily prohibit lane changes; treat them as 'do not cross unless you really need to'. Yellow lines (in either solid or broken form) separate traffic moving in opposite directions: broken yellow allows passing when oncoming traffic is clear; solid yellow on your side prohibits passing across the line. Double solid yellow prohibits passing in both directions.