But yes in theory once the new platforms open there will only really be a need for one platform in the existing train shed, AIUI the current P1 will be used for Northbound services rather than the existing P4 - no reason why they couldn't alternate between the two I suppose - at the very least the extra through platform will be useful during disruption. P2 and P3 have always been a bit unloved tbh but will continue to be used by Northern stock overnight I'd imagine. I wonder if there could be any scope for increasing trains to Bishop as a result of the layout change, you could pretty much have a self-contained shuttle going back and forth to/from P4 to bolster the service up to every 30 mins - whether there'd be the demand for it is another conversation.
Looking at a ~year-old Modern Railways article, the new layout retains the existing double junction, with diamond crossing, to the south of the station, which routes down main arrivals towards platform
#1 #4. With up mainline trains generally moving out of the train shed, Teeside trains can continue to arrive in or depart from platform
#4 #1, or the south bays, in parallel with such a down arrival if necessary, and now far less hindered by frequent up expresses, which will move to the new platform #5, outside the train shed to the east of the up main.
While the branch trains will still need to cross main line stopping traffic if using
#4 #1, whether terminating or running through to Teeside, they will be able to do so in two separate movements through the north and south junctions, either side of the station stop, each only interacting with one (stopping) mainline direction at a time. That's easier to path than securing a margin across both mains at the same time, especially under real-time running conditions.
Signalled passenger moves from down main south to
#4 #1 and the south bays will remain, though, as now, will require crossing over to the up main first for a short distance due to existing layout constraints. As these will likely be fairly infrequent or less critical movements, that continued limitation is likely acceptable. Platform
#4 #1 could become a useful reversing location for any new mainline local services terminating from the north, as the double ladder junction used currently for up expresses to weave over into the trainshed at the north end will remain, allowing an up local arrival to run into
#4 #1 at the same time as a down departure from
#1 #4 to the north.
Edit: Oh dear, I got confused by the new platform numbers into thinking they'd be in a consistent sequence across the layout with the old ones! All references to #1 and #4 transposed.
