What does two solid yellow lines down the center of a road signify?

Two solid yellow lines down the center of a road signify that neither lane of traffic can pass. This marking indicates a no-passing zone, which is typically placed in areas where visibility is limited or where road conditions make passing unsafe. The purpose of these solid lines is to enhance safety by preventing drivers from attempting to overtake others when it could lead to dangerous situations, such as head-on collisions.

In contrast, the other options suggest specific lanes or directions where passing might be allowed, which contradicts the purpose of the two solid yellow lines. The presence of such lines clearly creates a guideline that all drivers must adhere to, ensuring a safer driving environment for everyone on the road.