That's the datum line for when lower temperatures mean less grip from your tyres, because the compound they're made from gets harder.
And most drivers in Ireland don't use winter tyres, which compensate for this as well as dealing with other technical characteristics to cope better with the season. Tyre for tyre, the difference can mean a 5m shorter stopping time from 100km/h on a wet road, if you have winter tyres.
So take it a bit slower and leave yourself more distance from the vehicle in front. Even if the road ahead looks dry, or ice-free.
And at the risk of further repetition, get out and check your tyres regularly, especially these winter days.
Tread depth — at minimum 1.6mm and arguably twice that — along with inspection for cuts, crack and bulges, and for stuff caught in the treads and sipes. Pressures check at least every couple of weeks.
And, again, hang back a bit.
