I just think he came to grief on his way and his remains will be found one day, sadly.
That's the explanation that ordinarily would be most likely.
That said, the police thoroughly searched the roadsides alongside his most likely routes very early on. In fact, it was the first line of enquiry they pursued, including sending divers into Ampton Water, during the first week or two of the investigation.
The routes that were searched, including areas of woodland alongside the road, were:
BSE > Great Barton > Great Livermere > Troston > Honington; and
BSE > along the A134 to the turn-off for RAF Honington.
After that they searched along the sides of a number of other roads and came up empty handed.
I don't think it likely that he has been lying anywhere near any of his likely routes home, undiscovered, for over a year. This is an extensively farmed landscape, mostly under arable with a few pig farms. Farmers and landowners will have been all over their land in the 14 months since he went missing. Farmers will have ploughed, sewn, harvested and possible ploughed again since then. Landowners will have checked their patches of woodland, especially if they are using it as cover for game birds.
This is pretty typical of the landscape in the area:
https://www.google.co.uk/maps/@52.2...4!1scYka9Ci_gSJbpBk_puNXfA!2e0!7i13312!8i6656
There just aren't many places where a body could be simply lying about.