Which type of lines indicate that passing on the left is allowed in either direction when the way ahead is clear?

Broken yellow center lines indicate that passing on the left is allowed in either direction when the way ahead is clear. These lines are designed to inform drivers that they may safely cross the lines to overtake another vehicle, provided there is no oncoming traffic and it is safe to do so. This is important for maintaining traffic flow and allowing for safe overtaking in areas where visibility and conditions permit.

In contrast, solid yellow center lines denote that passing is not allowed, as they signify areas where it would be unsafe to overtake due to potential hazards or limited sight distance. Double solid yellow lines also indicate no passing; this reinforces the prohibition even more strongly. Dotted yellow lines generally suggest that passing could be permitted but are often used in conjunction with other signage or road markings that provide context to drivers about the possibility of passing.