Which sign shape is used to indicate a no passing zone?

The sideways isosceles triangle shape is used to indicate a no passing zone because it effectively conveys a warning to drivers about the prohibition of overtaking another vehicle in that area. This triangular shape is widely recognized, ensuring that drivers can quickly identify the no passing zone even from a distance. The point of the triangle typically faces the approaching traffic, making it intuitive for drivers to interpret the information being presented.

This design focuses on improving road safety by clearly communicating the risks associated with passing in hazardous areas, such as curves or hills where visibility is limited and passing could lead to collisions. The triangular shape stands out among other road signage shapes, which helps capture the attention of drivers when they need to be especially cautious.

Other signs, like the vertical rectangle, regular triangle, and circle, serve different functions or convey different types of information that are unrelated to no passing zones, which is why they are not correct for this specific context.