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His track doesn't look as if he went north of the road, but it's hard to tell because there are few transmission points--maybe he just went along those field boundaries past the footbridge and then used the various paths and roads between the two motorways? As a mountain biker, he won't have too much of a problem with going off-road for a bit if it means a significant shortcut.
Looks like there are lots of small roads parallel, and I think he must have walked/pushed down the drainage ditch and crossed on this footbridge https://maps.app.goo.gl/UHKGsrt74MuqdGQ57?g_st=ic