Here is an excellent explanation of the case for HS2. The interesting point made is that the Great Central alignment has a maximum top speed of 110 mph without tilt. But the speaker does not explain whether the whole route is so curvy that it would be limited to 110 mph throughout, or, if there are a few points which are speed-limited, and which could be straightened or by-passed, which would be an obvious thing to do if the route is reinstated. The East Coast Main Line used to have sharp curves at Offord and Selby, but the former was straightened by realignment and the latter by constructing a cut-off route.
The speaker also refers to the need to separate slow and fast trains. However,
The West Coast Main Line is four track all the way from London to Crewe, apart from the short section between Roade and Rugby, where the slow lines are routed through Northampton.
The East Coast Main Line is four tracks from London to Peterborough, apart from the Welwyn Garden City bottleneck.
The Midland Main Line, which could potentially run all the way to Manchester, used to have two additional tracks for slow train, all the way from London to Trent Junction, near Nottingham.
The speaker does not explain why a lower operating speed has not been chosen; the cost of building, equipping and operating a railway rises disproportionally once speeds rise above 100 mph. In the UK context, the optimum speed is probably between 125 mph and 140 mph.
One of the arguments for HS2 has been that the cost difference between building normal speed and high speed lines is very small. That is not conceivable.
Minimum permitted curvature limits the choice of route. For a conventional speed railway, old abandoned infrastructure can be used.
The case on time savings fails on diminishing returns and extra
terminal times when the service is only affordable if booking is made in
advance for travel on a particular time.
The case on capacity increase fails on the lower cost of building for 125 mph running.
The argument based on the WCML upgrade precedent fails on the grounds
that it was a more comprehensive scheme than just the provision of
additional tracks. The four-tracking of the Trent Valley line was
minimally disruptive.
Capacity shortage south of Rugby could be
relieved by reinstating the Great Central; additional works may be
needed at the approaches to London ie south of Milton Keynes, High
Wycombe and Aylesbury. Most of the trackbed between Aylesbury and Rugby
is still available.
The WCML is two-track between Roade and
Rugby, as the slow lines are routed via Northampton. There appears to be
space for an additional pair of tracks between these points; it would
require the construction of an additional tunnel at Kilsby.
In addition
There is already a second route between London and Birmingham: the GW routes via High Wycombe and via Oxford
There is a potential second route from London to Manchester: the Midland, which is four-track all
the way to Trent. Speed restricted sections with sharp curves have been
improved in recent years. Reinstating Ambergate to Buxton completes this, and adds useful local links
in the process.
Which is part of the point. If money is to be spent on
the rail system, it is better to invest in schemes which will improve
connectivity and journey opportunities, rather than on one big bang
project.
