There's something else to be thrown into the mix of why Avenues and "elbows" are where they are - the lie of the land. I seem to recall the first part of the Stonehenge Avenue up from the river seemed to follow the least steep route. (Might have been a dream though). That, followed by an aligned/ceremonial section could explain "the elbow". Maybe.

Then at Avebury, a lot of the WK Ave is situated exactly where the slope of Waden meets flat land (was Waden sacred, or wooded or separately owned or simply seen as sloped and therefore to be avoided?) Then. close to the Henge it kinks, so as to provide an impressive final entrance. Like Stonehenge's elbow?

I wonder if anyone has investigated whether at the other end, close to The Sanctuary, the route of the Avenue equates with the easiest route down the slope?