There are a lot of details lacking in the Blenheim picture.
There are "level crossings" on all current railroad crossings of roads in Britain, and I think there were back then too, though more often there were bridges taking the railways across the roads (often with a dip or cutting in the roads to take them under the railway, sometimes with an embankment to take the railway above the level of the road).
http://en.wikipedia.org/wiki/Level_crossing
The railway is now usually fenced off from fields, in the old days of the 1940s that would have been hedges, but almost nobody grows/lays hedges now, it's a dying folk craft, but in WW2 it would have been the main way of keeping one farmer's livestock out of another farmer's field, in a capitalist system, that matters.
http://en.wikipedia.org/wiki/Hedge_laying
I do hope this helps, I was really quite shocked to see this. Most of the time, where unused old railway lines crossed roads there were bridges, now sometimes taken down, sometimes where it was the road that went up over the railway, still in use even though there is no railway under them.