The lines running outside the trainshed at Darlington are Down Main, Up Main and Up Goods Loop. The speed limit on the mains at that point is 125 mph, although it reduces to 90 mph for a few chains over the Saltburn branch junction.
In the early 60s, the only daytime trains not to stop were the up and down Flying Scotsman (Scotsmen?), but there were some overnight trains as well.
A lasting memory is seeing a Tyne Dock 9F speed past hauling about 6 of the former South Tyneside EPB EMUs on their way to the Southern Region with a standard BR goods brake on the rear. It was running on Class H headlights, but way over 35 mph. I remember musing that it was a pity that the air pumps on the loco for operating the Tyne Dock - Consett ore wagon doors couldn't have been rigged to operate the brakes on the units!
When I used to spot at Newcastle Central in the 1950s heavy freight trains would go round the back of Platform 10 outside the train shed. As far as I recall they still do, although it's no longer Platform 10.
There were actually 4 goods lines past the back of Newcastle Central as this admittedly not very good photo of mine shows. The original outside wall of the station now has platforms 7&8 outside of it and there is a sort of by pass line which freight can use, though it just as often goes through the platforms.
The avoiding lines at Northallerton are, of course, the original Leeds Northern main lines. The mileposts from Northallerton all the way to Gateshead via Hartlepool are still from Zero at Leeds (I think Wortley Jc, but stand to be corrected on that) via Harrogate and Ripon. In the 1960s, I remember seeing some very basic platforms adjacent to Boroughbridge Road level crossing, but I'm not sure they were in use at all.
There is 1 passenger train booked that way, Sundays 1P77 - 13:36 Manchester Airport to Redcar Central, in addition there is an early morning York - Redcar Central ECS working.