(5 hours ago)Storx wrote It's all deckers on the 34 mostly. No use for the 4 unless you want to smash it into the bridge at Fatfield.

Why would they stick a decker on the 4?

The gaps are huge on the 34. Solos being reallocated from the 4 to the 34 would surely be the easiest option. 

Minimal impact on the 4.
Problems solved on the 34.

The bridge at Fatfield is fine for a decker. 
It's the tunnel at Penshaw that has the height restriction.