What does a solid line indicate in terms of lane usage?

A solid line indicates that drivers should not change lanes. This is a crucial safety measure, as solid lines are typically used in areas where lane changes could be dangerous, such as near intersections, pedestrian crosswalks, or on sections of road where visibility is limited. By instructing drivers to stay in their current lane, the solid line helps to prevent accidents that could occur from sudden lane changes in these high-risk areas.

The other options suggest actions that are not permitted or regulations that are unrelated to solid line markings. For example, passing is only permissible where a dashed line is present, and a solid line does not designate parking zones or indicate speed limits. Therefore, recognizing the significance of solid lines is essential for maintaining road safety and obeying traffic laws.