Deer may be an escalating issue - they are often rather more agile and determined than the average domesticated animal and the numbers around can be rather greater than people might notice.
It is said that there are actually more deer about now than at any time since the end of the last Ice Age.
https://www.bbc.co.uk/news/science-environment-21688447
The scale of the lineside fencing in Ireland seems generally a lot more 'discrete' than on the Big Island.
I live near a 'wild patch' and we have quite a few deer-related road traffic incidents, about three or four a week - I've witnessed a couple and the damage to the vehicles was very dramatic, although no occupants were significantly injured in either.
When I first moved here, in the mid-70s, I lived in digs and the phone number was almost the same as the one that you would ring for the Warden who dealt with the aftermaths, just the last two numbers reversed. We would get a false 'alert' every few weeks, usually after the pubs had shut. I remember being woken once, in the early hours, by my landlord answering the phone to a rather inebriated driver who had got a deer stuck through his windscreen - "Well, if it's still alive, give it the kiss of life and take it to the A&E"
I often wonder what happened...