[alancalverd (OP)]

I'm wondering whether new railways really make ecological sense. To make and lay four rails (one track in each direction) on ballast, without taking into account any landscaping or trackside equipment, my estimate is about 1000 tonnes of CO2 emitted per mile of new track.

I'd be grateful for any refinement of the figures. My estimate is based on 300 kg concrete sleepers laid at 0.8 m separation and 60 kg/meter of steel rail, plus an allowance for bringing the materials to site by road.

Assuming you already have the vehicles to hand, how many train journeys must be made before the total CO2 emission is less than making the same journey by plane?

And the CO2 footprint of the vehicles themselves?   

[syhprum]

It would be great fun if we all had small aircraft to go everywhere as was envisaged in Edwardian times , it might work in a near empty country like Australia but imagine the number of crashes if every motorist or rail commuter changed to a light aircraft 

[alancalverd (OP)]

I'm thinking of 200-seat turboprops flying on scheduled intercity routes.

[Bored chemist]

I'm thinking of 200-seat turboprops flying on scheduled intercity routes.

I'm thinking of people who don't live in cities.

[alancalverd (OP)]

Time was that the UK had lots of active branch lines serving small communities, all scrapped in the name of progress by Dr Beeching (his textbook on neutron scattering, however, remains a useful reference). Resurrecting a single track, or even pouring concrete over it and running a bus, may make some sense. But government vanity projects are all about new high speed rail links between urban centers and as you have pointed out elsewhere, these are intended to bypass the smaller stops.

So the valid question is whether the carbon dioxide footprint of such projects as HS2, which you imply have no social value and I have pointed out have no value to businesses in other cities,  is defensible?   

[Bored chemist]

But government vanity projects are all about new high speed rail links between urban centers and as you have pointed out elsewhere, these are intended to bypass the smaller stops.

I pointed out elsewhere (as you say) what they are actually for.
Why call them "vanity projects"?
In particular, given that Boris, the vainest of politicians, is thinking of scrapping HS2, how could it be a vanity project?

projects as HS2, which you imply have no social value

That's the opposite of what I said.

I have pointed out have no value to businesses in other cities,

That's just wrong.

[alancalverd (OP)]

1. Vanity is not always transferrable between administrations

2.

I'm thinking of people who don't live in cities

HS2 doesn't stop between cities, so it is of no more use to those who don't live in cities than a plane that flies between cities.

3. The journey time from e.g. Cambridge to Birmingham will not be shortened by HS2 - the bus is quicker and cheaper because it doesn't spend the first 60 miles going the wrong way then crossing London. Similarly from anywhere north of Harlow or west of Reading.

[Bored chemist]

HS2 doesn't stop between cities, so it is of no more use to those who don't live in cities than a plane that flies between cities.

Still wrong (for the reasons I gave earlier).
Repeating it doesn't make it right.

The journey time from e.g. Cambridge to Birmingham will not be shortened by HS2

That's roughly as stupid as saying that the Channel Tunnel doesn't improve the journey time from manchester to Liverpool.
Of course it doesn't.
That's not what it was for.

[alancalverd (OP)]

Precisely. So what is HS2 for? To reduce the journey time between London and Birmingham by about 15 minutes, at a cost of £5000 to every taxpaper, nearly all of whom will never use it. I very much doubt that the northern sectors will ever be built.

The Channel Tunnel is quite a different kettle of fish. It carries a lot of freight (important for business) and shortens the journey time from everywhere in Great Britain to everywhere in Europe south of Denmark (Harwich-Hook ferry has a slight advantage for the northern areas)

[Bored chemist]

So what is HS2 for? To reduce the journey time between London and Birmingham by about 15 minutes, at a cost of £5000 to every taxpaper,

Still no.
Have  you really forgotten already?
I guess you are getting old.

The point of HS2 is not actually to get people from London to Birmingham half an hour quicker. That would be silly.

Once you realise that, it makes rather more sense.

(The astute will realise I should have added "and back".)

Why are you still attacking the straw man idea that the 15 min reduction in B'ham to London travel time is the purpose of HS2?

Were you hoping that nobody would notice that you are using a logical fallacy to try to promote a view that doesn't make a lot of sense?

Is that why you started another thread?

[alancalverd (OP)]

Why are you still attacking the straw man idea that the 15 min reduction in B'ham to London travel time is the purpose of HS2?

Because no other facts have been attached to the project proposals. Plenty of airy-fairy talk on the official website about serving 25 towns, 24 to the north of Brum, but no actual commitment yet, and the cost of the first bit (no stops between London and Birmingham) is already out of control. And the saving on short journeys (e.g. Birmingham to Nottingham) is trivial.

But my original question for this thread was whether new railways of any sort are actually carbon-efficient. Running an existing  train on existing track may well have a very small carbon footprint per passenger mile, but what is the carbon "capital" investment in making a track and a train, and how does that compare with other means of public transport?