So all reopenings should be specced for high speed operation as a matter of course then?
Paying for overhead line equipment and Class 395s won't significantly increase the cost of a scheme that will inevitably cost £30m/mile anyway.
No - what I’m saying is that in building new railways, of which I have done a few, the difference in cost between a twin track high speed railway, and a twin track “regular” railway, is surprising little.
All the pre-construction costs are essentially the same: feasibility, development, consents, design, land purchase - it doesn’t matter what sort of railway you build, these are to all intents and purposes identical on a per mile, like for like basis. This can represent between a quarter and a third of total costs.
Within construction, many of the costs are the same - site compounds, project management, drainage, utilities, highways, traffic management, earthworks, over bridges, environmental mitigation. This is another quarter of the costs or so.
More of the construction costs have, frankly, small increments for high speed - under bridges, formation, track (essentially a little more ballast), electrification (if provided, obvs), signalling.
At the end of construction, testing, commissioning, entry into service an demobilisation is no different for high speed rather than regulars railways. This is about 10% of costs.
All told, around 70% of the costs are the same, and the remaining 30% have an extra 10-30% for high speed. So about 10% difference overall.