Final answer:
Crossing solid white lines that separate lanes of traffic moving in the same direction is generally discouraged and may be illegal. It implies that lane changes are unsafe or should not be performed. Always check local traffic laws for specific regulations.
Step-by-step explanation:
When solid white lines separate lanes of traffic moving in the same direction, crossing a solid white line is generally discouraged and could be illegal, depending on the traffic laws of the jurisdiction. Solid white lines are used to denote lanes where lane changes are considered unsafe or are not to be done for certain periods, such as in construction zones or near freeway exits.
While in some places you may legally cross a solid white line, it is advised to do so with great caution. It is important to always check the specific traffic laws of the area you are driving in, as these can vary.