What does a blue sign with a red cross mean?

A blue sign with a red cross indicates that vehicles are not permitted to wait for any reason. This type of signage is essential for regulating parking and waiting, particularly in busy areas or where it is important to keep traffic flowing smoothly. The red cross serves as a clear prohibition for drivers, signaling that stopping or waiting in that area, regardless of the circumstances, is not allowed. This signage helps maintain safety, prevents congestion, and ensures that designated areas remain accessible for other road users.

The other choices suggest alternative meanings that do not align with the established traffic signage conventions, which is why they are not applicable in this scenario.