http://maps.google.co.uk/maps?hl=en&....36 ,,1,11.01

At the point where the road used to go over the canal basin, the road still
has a lengthy bump, but the pavements are banked up a foot or two higher at
the centre. I can't see any reason why the pavements would have been banked
up over the road when the canal basin still stretched under the road. It
looks as if the road used to be higher than now, but I can't imagine that it
would be possible to lower a road on a bridge while leaving the bridge
intact. So the part of the bridge carrying the road was demolished and the
gap beneath it filled in with earth, and the road reinstated at a lower
level.... the parts of the bridge carrying the pavements were left intact,
and still carry the pavement some way over the lowered road. But that seems
bizarre too.... surely if you're going to demolish the road part of the
bridge, you'd demolish the pavement parts too.