What should a driver do when approaching a roundabout?

When approaching a roundabout, the correct action is to yield to traffic already in the roundabout. This is crucial for maintaining a smooth flow of traffic and ensuring safety within the roundabout. Traffic in the roundabout has the right of way, which means that vehicles entering must wait for an appropriate gap before proceeding. This yielding process not only helps to avoid collisions but also facilitates efficient navigation of the roundabout as vehicles can enter seamlessly without disrupting the flow.

The other choices present actions that could lead to dangerous situations: increasing speed can create a higher risk of accidents as drivers may not be prepared for other vehicles in the roundabout, stopping unnecessarily could block the flow of traffic, and ignoring signs can lead to disorientation and confusion, which are particularly hazardous in complex driving environments like roundabouts.