I found these pictures of the cattle guards I use - - - cost next to nothing and will handle any load the road will handle.
The tennis balls get moved around some with traffic but you can just slide them back.
This is an end - - - I have a treated 2X6 top and bottom of the rubber belt at both ends. Run the wire ( three strands works well ) to the other end and hook up to electris fence.
The cattle come up to eat the "apples" tennis balls and after that they will not cross a rubber belt laid anywhere! I keep dogs, cattle and horses in with these.
Just don't let your wife try to mow them as it causes a mess!
These have been in use for about 5 years with very little maintance and no escapes at all. I had to put in a pipe walk thru gate for the dogs. If I want to move cattle thru there I just un hook one end and slide the belt off to the side and cattle will go willingly as the belt is what they fear!