Final answer:
A posted speed limit of 55 mph is the maximum legal speed for that road. There may be slight enforcement tolerance, but exceeding this can result in a traffic violation due to the accuracy of radar devices used by law enforcement.
Step-by-step explanation:
A posted speed limit of 55 mph means that this is the maximum legal speed at which a vehicle may travel on that particular stretch of road. It is a de jure regulation, meaning it has been established by law. However, there is often a slight degree of enforcement tolerance, as it’s recognized that speedometers can have a small margin of error, and thus traveling a bit above the limit might not necessarily lead to a citation. Nonetheless, exceeding the speed limit by a significant amount can result in a traffic violation ticket as law enforcement agencies use radar devices which are highly accurate. It's important to understand that this enforcement discretion does not officially change the legal speed limit; safety and legal compliance should always be the priority.