What is restricted by a "No vehicles over height shown" sign?

The correct answer indicates that vehicles over a specified height are prohibited by a "No vehicles over height shown" sign. This type of sign is crucial for ensuring safety and preventing damage to both vehicles and infrastructure. The sign specifically alerts drivers about the maximum allowable height for any vehicles passing through an area, such as under a bridge, in a tunnel, or within a restricted zone.

If a vehicle exceeds the height limit displayed, it could become stuck, cause an obstruction, or even result in an accident. Thus, it is essential for drivers, especially those operating larger vehicles, to heed these warnings to avoid such dangerous situations.

The other options do not accurately capture the intent of the sign. For instance, only allowing buses or requiring all vehicles to adjust their height does not reflect the prohibition of specifically tall vehicles, while limiting pedestrian access based on height is unrelated to the purpose of this type of signage.