In the motorcycling world a roadrace circuit has a formed surface and has both left and right hand turns. Historically the surface can be almost anything from rolled and oiled dirt to modern hotmix. But it's as smooth as possible.
It's quite distict from a motocross cicuit which should have a "natural" surface - albeit often roughly graded.Usually including jumps.
The Irish "real roads" circuits these days are an anomaly. I think Ireland and NZ probably have more surviving than anywhere else. sadly I suspect their days are numbered.
Spyda knows more about the Seagrove setup than me,