What does a dashed border on a traffic sign indicate?

A dashed border on a traffic sign typically indicates that the sign applies specifically to a certain class of vehicles, which may include heavy vehicles. When you see a traffic sign with a dashed border, it usually signifies restrictions or rules specifically intended for larger vehicles, such as trucks or trailers. This differentiation helps ensure that drivers of heavy vehicles are aware of regulations that they need to abide by, which might not apply to regular passenger vehicles.

In contrast, the other choices describe categories or conditions unrelated to the dashed border's specific purpose of indicating that the sign is directed towards heavy vehicles. Thus, the characteristic of having a dashed border clearly communicates that the regulations or cues provided by that sign are especially relevant for drivers operating heavy vehicles, ensuring safety and adherence to road laws specific to those larger vehicles.