How about:
2 LH in column in DGo (difficult going).
The front LH is on a road, facing along the road.
However, the road turns a corner behind the front LH, so the second LH is not on the road.
The move will be a march.
If they move at road march speed, both elements will end out of the DGo, otherwise at least will end inthe DGo.
The way I think this works, the rear LH is not moving entirely along the road, so the column moves at DGo speed. Is that right?