Which lane marking should a driver not cross when it is solid?

A solid yellow line indicates that passing is prohibited for drivers on that side of the road. This marking is used to separate lanes of traffic moving in opposite directions, signaling to drivers that they should not cross over into the opposite lane to overtake another vehicle. This restriction is critical for maintaining safety on the roads, as passing in such areas can lead to head-on collisions.

In contrast, dashed white lines allow drivers to switch lanes or pass other vehicles when it is safe to do so. Similarly, a dashed yellow line signifies that passing is permitted, provided it's safe. A solid white line generally indicates that lane changes are discouraged, but it's not as strict as a solid yellow line for opposing traffic. Understanding these distinctions is vital for safe driving and adherence to traffic laws.