You must not pass on two-lane highways in all of the following situations EXCEPT:

In the context of passing on two-lane highways, a dashed yellow line on your side of the center dividing line indicates that passing is allowed in that area. This marking is specifically designed to inform drivers that it is safe to overtake another vehicle, assuming that it is safe to do so and there is no oncoming traffic.

Understanding the implications of the other scenarios helps illustrate why passing is restricted in those cases. A solid double yellow line indicates that passing is prohibited, as it ensures the safety of vehicles in both directions. Similarly, when there's an approaching vehicle from the opposite direction, safety is compromised if a driver attempts to pass. Lastly, if a road is designated with markings for no passing, it is a clear indication that such maneuvers should not be attempted. Thus, the presence of a dashed yellow line signifies a safe opportunity to pass, differentiating it from situations where passing is frowned upon due to safety concerns.