Kings Dyke Bridge or Tunnel

Just been asked – why is there tunnels showing on the latest plans.
I was to believe that a tunnel under the railway was being built for Forterra (Brickworks)
to make it easier for them to transport materials from one side to the other without impacting the road/bridge – I maybe wrong…..however if this is the case, maybe do away with a bridge entirely and build a Bigger Tunnel…….Then there is the cost….are Forterra paying for this to be built! – remember they are one of the landowners who will have benefitted from selling their parcel of land …..and maybe get a ‘free’ tunnel thrown in as well.
Never mind the commercial sensitivity of all of this…..at some stage ‘transparency’ of what’s been going on will all come out…..by which time – it may well be forgotten about…