I've read the paragraph several times and maybe it's my ESL, but I don't quite follow. Is the term "Grade" here used in the "Slope" sense, as in don't run the

I've read the paragraph several times and maybe it's my ESL, but I don't quite follow. Is the term "Grade" here used in the "Slope" sense, as in don't run the cars up and down the hill? And if that's the interpretation, I don't necessarily agree with the next point that obstacles are reduced on slopes/hills... so I probably am not following correctly :-/ Thanks!