Roundel vs Roundabout [closed]

In Britain, a roundel in this context is the white circle in the middle of a mini-roundabout. This one is fairly large, since it's bus-size:

^{[from Surface Markings Ltd]}

Traffic is to circulate around the white blob as though it were a full-size roundabout [see below], and only go over it if that is unavoidable — as it would be for the bus turning right. Roundels can often be slightly humped, or simply painted on the road as here.

From a report on Lexology.com (my emphases):

Mr Starks reached the roundabout first, entered it and began his right turn, taking a line which involved passing over the top part of the roundel. PC Richardson entered the roundabout very shortly after him. She did not moderate her speed or her course in any way and was taking a line that involved passing directly over the middle of the roundel. She struck Mr Starks’ car in the centre of the junction.

A roundabout is rather larger, and the centre is not designed to be driven over:

^{[from Aubrey Dale via Wikipedia]}

Just for completeness, roundel is also used to refer to the Underground sign adopted by Transport for London

^{[London Underground via TFL]}

and particularly to RAF plane markings (and derivatives in Commonwealth realms' air forces such as the RCAF, RAAF and RNZAF)

^{[helluvit Sports Car Club]}

A "roundel" is any circular design, for example used by many companies and air forces to identify themselves. Wikipedia has a number of examples of military and non-military usage.

In this context, the roundel refers to the painted circle in the middle of a small roundabout (such a roundabout is usually referred to as a "mini-roundabout"). However, I've never heard it referred to as such: unless you need to specifically talk about the painted road markings, rather than the road layout itself, you'd talk about the roundabout, rather than the roundel.