Under which condition is it illegal to pass on a two-way roadway?

Passing on a two-way roadway is illegal under any of the conditions listed because safety is the primary concern in each situation. When approaching a curve, visibility is often limited, making it difficult to see oncoming traffic, which increases the risk of a collision.

Near a railroad crossing, the danger comes from the possibility of an approaching train that may not be immediately visible. It's crucial to remain in your lane, allowing you to safely navigate the crossing without risking an accident.

Similarly, when approaching a bridge with an obstructed view, you may not be able to see other vehicles or obstacles in your path, again increasing the chances of a crash if you attempt to pass.

Each of these scenarios underscores the importance of maintaining safe driving practices to protect yourself and others on the road. Therefore, it is illegal to pass in these situations to promote safer travel for all users of the roadway.