(c) Pete Glastonbury
Click to enlarge - larger version available - just ask.
The red arrow shows the direction of the Winter Solstice Sunset from Stonehenge - an alignment that UNESCO says should be protected. The orange and lilac lines are the options for the roads and the blue circle the portal position.
I think that you have put together an excellent overview with your various blogs on this subject.
In the end it is up to individuals to decide whether they wish to submit comments to Highways England. It is one thing to just state that one objects with general reference to the potential detriment, but volume of objections is often way down the list of importance. It is the specific scientific evidence which will decide, bearing in mind that a decision in principle has already been made and only two options are on offer. I guess it is beyond most average person's ability to submit the detail that is required, if even they are aware that it exists, to sway the decision one way or the other, or rejection of the tunnel proposals altogether.
Since I have been involved in both EIA and LVIA professionally, I suspect that the southern option is preferred, and the potential visual intrusions already understood. So, and again I am guessing, the next best option - the northern route - offers some acceptable engineering alternatives otherwise it would not have been included. Alternatively this may be an equally preferred - or better - option, but elimination via a public consultation of the aesthetic impacts of the southern option offers a way of passing the buck should problems arise during and after construction.
From a professional eye view, I can see things which haven't been mentioned, which impact whichever option is chosen. Moving the tunnel portal, even a short distance to the west, as suggested by CBA, will in fact make things worse, and moving a lot further west will introduce a whole new arena of impact on environment and people, as well as cost implications and review.
For this reason, and even though I am now retired from professional involvement, I am preparing a personal submission, but this will be purely on objective scientific issues concerning the location of the western portal, the most important as far as my current archaeoastronomical interests are concerned.
It will be interesting to know if any of your other readers, have or are preparing submissions.