Joe, I don't think that's right, although I concede that it's similar in parts. At home on a holiday CD anthology, I have a recording of a song with exactly the same tune as Kemp's. I'll get you that info when I can, together with whatever background is offered on the liner notes (if any). I don't know offhand if the other song is older or newer.
This next, I can tell you with a fair degree of authority due to having heard Ms. Prior introduce the song in concert with this anecdote: Rick Kemp wrote SAtR one foggy or stormy night when one or the other of them was very late returning to their mutual home from a gig, via a twisty, hilly road that required very careful navigation. I believe Mr Kemp was the waiter rather than the driver and wrote it to keep himself from worrying about her, but am not entirely sure. (It was a long time ago.) At any rate by the time whoever was driving finally arrived home, the song was finished. So although it sounds very religious in tone, what it is about is that one of the couple was, literally, waiting somewhere along the (obscured by weather) road for the other to return.