Under what condition is passing allowed on a highway?

Passing on a highway is primarily allowed when the road markings indicate that it is safe and legal to do so. When both sides have broken yellow lines, it signifies that passing is permitted in both directions. This marking indicates a clear, unobstructed path to overtake another vehicle.

In contrast, if both sides have solid yellow lines, it means passing is prohibited due to potential dangers, such as limited visibility or a high likelihood of encountering oncoming traffic. The presence of a speed limit above 50 mph does not directly dictate whether passing is permissible; rather, it's more about the road markings and conditions. Additionally, simply having no other vehicles in sight does not guarantee that it is safe to pass; it is essential to assess the overall conditions, including road configurations and potential blind spots.

Thus, the correct condition for passing on a highway occurs when both sides have broken yellow lines, as these lines specifically communicate that it is safe to pass under those circumstances.