What is indicated by circular-shaped signs that have a blue background?

Circular-shaped signs with a blue background are used to indicate obligations or mandatory actions that drivers must follow. These signs typically convey instructions that are required by law, such as "Mandatory Turn" or "Bicycle Lane Ahead." The blue color specifically denotes a positive command, meaning something that must be done rather than something that is restricted or forbidden.

In contrast, signs that warn of danger usually have a different shape and color scheme, such as triangular signs with a red border, and prohibition signs feature a red circle with a diagonal line across an image or symbol to indicate what is not allowed. Information signs, which provide guidance or directions, often utilize rectangular shapes and various colors depending on the type of information being conveyed. Thus, the distinctive characteristics of the circular shape and blue background clearly signify a requirement for compliance, making obligation or mandatory action the correct interpretation.