Thank you. Reopened at my request as Highways England is proposing to dual the A46 Newark bypass and conducted a consultation last year (now closed):
The A46 Newark Bypass is an important route connecting the M1 and Leicester to the A1 and central Lincolnshire.
highwaysengland.co.uk
(If it shows "+ Public Consultation 2020" at the bottom, click on that and more details will appear.)
I always imagined that any rail flyover would run immediately alongside the SE side of the Nottingham-Lincoln line. There seemed to be just about enough space for both that and the dualling of the A46.
There are two options for dualling the road, shown in the two "maps" and in more detail in the two "drawings". Both include a grade-separated road junction towards the north end of the road that seems (from the "drawings") to use up all the space between the road and the Nottingham-Lincoln line, apparently meaning that any future rail flyover would need to be on the other side of the line.
According to the "environmental constraints map" there is a local wildlife site on that side of the line further south.
Presumably HE will have had to consult NR - I wonder what NR said?
I haven't read the "options summary report" yet.