This is what I do not understand. They could theoretically have split the Southport service at Wigan from the May timetable change, with 3/4 car EMUs between Oxford Road/Stalybridge and Wigan North Western, and a DMU shuttle from the bay platform at Wallgate. And/or the Leeds to Wigan Wallgate service could be extended to Southport (they have over an hour turnaround in a siding at Wigan as things stand, which is hardly efficient diagramming). While this would result in a slight reduction in diagrammed coaches on some Wigan-Manchester trains, it would be far better than the current situation, where they are short formed more often than not.