Question Topic: Road and traffic signs
Explanation: Signs in the shape of a circle give orders. A sign with a red circle means that you aren't allowed to do something. Study Know Your Traffic Signs to ensure that you understand what the different traffic signs mean.
Category: Road and traffic signs
References: The Official DVSA Guide to Driving: Section 6, Highway Code: Page 106, Know Your Traffic Signs: Page 9, Know Your Traffic Signs: Page 16