When is it illegal to pass another vehicle?

Passing another vehicle is illegal when the line that divides traffic lanes is solid. A solid line indicates that it is unsafe to change lanes or pass because doing so could lead to a hazardous situation, such as colliding with oncoming traffic or not being able to see oncoming vehicles due to curves or obstructions. Compliance with lane markings is essential for maintaining safety on the road.

The other options do not inherently create an illegal passing situation. For instance, traveling downhill does not automatically make passing illegal; it depends on visibility and road conditions. Similarly, other vehicles may be parked without affecting the legality of passing unless it specifically interferes with the traffic flow or safety. Finally, the time of day—whether it's night or day—does not alone dictate the legality of passing, as passing laws relate more to the visibility and road markings than the time. Therefore, understanding the meaning of lane markings is crucial for safe and legal driving practices.