Apologies for all the questions but once Roby - Huyton is remodelled roughly how many miles of 90mph running will there be?
Is there any scope for this to ever be further increased? What are the key differences in engineering for 90mph compared to 100mph, my feeble knowledge would imagine it to be minimal?
According to the NR plan, the speed will go up to 90mph east of MP3 (after the Olive Mount chord runs in), so another 4 miles.
So there will eventually be 18 miles at 90mph (Olive Mount-Astley) with the rest at 75mph.
A 3-mile stretch over Chat Moss was only 60mph, and some of it still is - I'm not sure if/when this will change.
To go from 90 to 100 is more difficult than it sounds.
I'm no expert, but you usually have to upgrade the signalling and level crossings, as well as the track and the OHLE (though the new stuff is supposed to be good for 100mph).
Embankments might need strengthening, and the section over Chat Moss is never going to be fit for high speed as it essentially "floats" over the bog.
Looking at the line as a whole, the bottlenecks will still be at each end, with slow sharply-curved layouts Ordsall Lane-Victoria/Piccadilly and Edge Hill-Lime St.
Both are due to be remodelled soon, but speeds will never be high.