Speed limits. Yes they are there for our safety but the tinkering they've done with them on some roads lately is ludicrous.
My commute takes me through two villages 3 miles apart. Nice wide road, nothing but fields either side, no pedestrians. Until a couple of years ago was 60 mph all the way between them and you could do it perfectly safely.
Now it's 50 for one mile, down to 40 for another 1/2 mile for no obvious reason, then back to 50, then the 30 limit for the next village now starts half a mile before you reach it!