John B wrote:
On 11 Oct, 20:02, wrote:
But a new conventional 225km/h line to Manchester might be enough,
offering about 1h45, and the same argument could apply elsewhere.
Maybe only the Scottish run really needs more. Britain is smaller than
France or Spain, and thus the gains to be achieved from building LGVs
are proportionately less, particularly within England alone.

I'd be interested to see any studies on the cost per km of a new 225km/
h line versus the cost of a new LGV - and rather surprised if they
were significantly different.

The other issue no-one has mentioned is the cost (amount of energy) used
per mile of high speed rail travel compared to medium speed. With
efficient regenerative braking, most of the energy used is to overcome
friction, which rises with the square of speed - i.e. up to twice as
much energy is needed to go at 200 mph compared to 140 mph. This matters
because the main reason for preferring rail to air is reduced CO2 emissions.

Admittedly it's easier to power trains than planes from non-fossil fuel,
but it's going to take a long time to get all our electricity from
renewable or nuclear sources.

I think 140 or 150 mph rail is fast enough for the UK. But that needs to
cover a lot more than a few principal routes, so that overall journey
time is not clobbered by 20 or 30 slow miles at each end.

The other factor in overall journey time is frequency - it's not much
use getting to Edinburgh in 2 hours if you have to wait another 2 hours
for the train to leave. That means we need increases in rail capacity as
well as line speed.

Colin McKenzie

--
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