The Skerries is (I figured and confirmed) a road race on public roads, not unlike the IOM and some other events like that in parts of Europe. Seems that many racers lose their lives or sustain serious crashes in these kind of races, for a multitude of reasons.
It is no wonder that most high level professional road racers (MotoGP) are banned from participating in these events by their contracts. Of course our own Nicky Hayden died riding a bicycle (with extenuating circumstances).