https://maps.google.com/maps?ll=51.5...87.97,,0,-0.42

This road reminds me of various roads in the Lea Valley that pass
between two reservoirs, but it doesn't look like like there are, or
were, reservoirs here. It seems odd that they would have cut the road
through a natural ridge unless it was a high speed road, which it isn't.
So the alternative is that the land either side has been raised since
the road was built. Is it a dumping site for Crossrail spoil?