When the M621 urban motorway was built by Leeds City Council in the early 1970s the open public space of Holbeck Moor was sliced in two by the motorway. This wide subway was provided to mitigate the severance of the open space.
Re the comment that the crane driver might be able to get some good pics for geograph. As with aerial shots, he would probably be accused of viewbagging, which is frowned on, & rightly so. (Viewbagging is when a picture is taken from a long distance outside the square to which it is attributed.)