What is the meaning of a mandatory speed limit sign?

A mandatory speed limit sign indicates that the speed limit it displays is legally enforceable. This means that drivers must adhere to the specified speed limit, and failure to do so may result in legal penalties such as fines or other consequences. The purpose of this sign is to ensure safety on the road by maintaining a consistent speed that is deemed safe for the conditions and type of roadway.

The other choices present incorrect interpretations of what a mandatory speed limit sign conveys. An advisory speed limit is merely a recommendation that may change based on road conditions and is not legally enforceable. Saying the speed limit is optional does not capture the seriousness of adhering to posted limits, implying a driver may choose to ignore it. The statement that no speed restrictions apply incorrectly suggests that drivers have no legal speed limits to follow, which contradicts the purpose of such signs.