My entrance is 60 ft off the highway and 25 feet wide. I've had severarl semi trucks with 40 foot trailers in here and they always come close to one or the other gate post. I sometimes wonder if there is such a thing as wide enough because somebody is always gonna cut it close and risk hitting it.
A little off topic, but when talking to owners of RV Parks, the biggest complain that I hear over and over again is that nobody can drive. Too many of them cut the corners too tight when turning and don't realize that thier rear ends will turn even sooner. The longer they are, the worse it is. My Dad has been RVing since the early 1970's and has an allot of miles on them. He's also guilty of cutting corners too close and has had to back out a few times and try it again. It just happens.
My thought on this is to crown the road down the middle and have my drainage ditches wide and shallow. I expect people to hit the road right with the front tires, but know that the back ones will wonder off into the ditches from time to time. Having a wide V at your entrance will solve all your problems if you can get people to aim for the middle of the drive when they make the turn. If they have a flat, smoot way in that they can cut the corner as soon as they get past the first fence post, that's just what somebody will do. It only takes one person to make the mistake and ruin your fence, his vehicle and your day.
At 60 feet off the highway, I'm just barely far enough. 50ft might be a little tight when I have my 16ft trailer on my truck. It's way too short for my parents RV when they are towing thier exporer. When they show up and the gate is closed, they have to park across the road and walk to the gate to open it. 50ft sounds like allot, but it's not. 80 ft is what I should have set mine at and 100 feet would be even better.
Eddie