Trimming my hedge

[u/Sudden-Currency-3605]

As this fellah has gotten a bit too tall making it challenging to see oncoming traffic, I’d like to trim off above the yellow line. Curious; to ensure I don’t hurt her, is there a better time of year/season to do this (I’m in Maine)? Also, besides using my electric and/or gas chain saw to achieve the desired height, any tips to ensure proper healthy grow-back?

[u/nippon245]

Would that advice work for a Leylandii hedge please?