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I think it is pretty straight forward.

Rail has its main emissions during the construction phase of the rail, flight during start and landing of each plane. So I think the cutoffs are not based on distance but rather on number of passengers on the line.

Searched back in previous discussions and found this to support my view:

OECD/ITF: JTRC Discussion Papers

Environmental aspects of inter-city passenger transport
Per KAGESON, Nature Associates, Stockholm, Sweden
Discussion Paper No 2009-28, December 2009

Page 25 in the pdf:

The conclusion of this paper is that investment in high speed rail is under most circumstances likely to reduce greenhouse gases from traffic compared to a situation when the line was not
built. The reduction, though, is small and it may take decades for it to compensate for the emissions caused by construction. However, where capacity restraints and large transport volumes justify investment in high speed rail this will not cause overall emissions to rise.

In cases where anticipated journey volumes are low it is not only difficult to justify the investment in economical terms, but it may also be hard to defend the project from an environmental point of view as it will take too long for traffic to offset the emissions caused by building the line. Under such circumstances it may be better to upgrade an existing line to accommodate for somewhat higher speeds as this would minimize emissions from construction and cut emissions from train traffic compared to high speed rail.

Note though, that it mainly compares HSR and ordinary rail.

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by A swedish kind of death on Tue Jul 19th, 2011 at 03:20:24 PM EST
[ Parent ]
Thanks for this.  But would I be right in thinking that the environmental advantage of HSR over air transport is marginal except at high volumes of traffic on a route?

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by Frank Schnittger (mail Frankschnittger at hot male dotty communists) on Tue Jul 19th, 2011 at 03:28:19 PM EST
[ Parent ]
I do not know what the cutoff is, but yes something along those lines.

And now I see that the pdf is gone from the link. I copied the quote from the comment I wrote when I read the paper.

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by A swedish kind of death on Tue Jul 19th, 2011 at 03:40:24 PM EST
[ Parent ]
More than just the enviormental benefit, one of the main points of HSR.. and regular rail, for that matter, is that it is a mode of transport not dependant on oil, but instead largely electricity. Yes, for construction too. - arcfurnace steel is a fairly economically viable proposition. This reduces the amount of very expensive synthetic fuels we are going to need in the long term. This also implies that once the problem of producing abundant low-carbon electricity is solved, rail construction itself gets much less polluting, because the carbon footprint of the steel drops.

There are also cement chemistries that are outright carbon negative as they absorb more carbon during hardening than it takes to produce them, so the carbon foot print of rail is not unavoidable. The physical  footprint however, is really quite difficult to avoid or reduce except by going entirely below ground or with elevated tracks.

by Thomas on Tue Jul 19th, 2011 at 04:19:36 PM EST
[ Parent ]
by Frank Schnittger (mail Frankschnittger at hot male dotty communists) on Tue Jul 19th, 2011 at 04:38:22 PM EST
[ Parent ]
Airports have a huge footprint too.
by njh on Tue Jul 19th, 2011 at 10:42:11 PM EST
[ Parent ]
I think I commented when askod posted this earlier that I don't think any simple claims can be made. We are talking about factors here that each have ranges in orders of magnitude:

  • High-speed line electricity supply: it obviously makes a difference whether it comes from coal-fired power plants or hydro, for example.
  • High-speed line construction emissions: with the same materials technology (because most CO2 emissions are from manufacturing steel and cement), it basically depends on the volume of superstructures, and there is a great difference between a line consisting of level track on flat stable ground in a sparsely populated area and a line consisting almost only of viaducts over soft soil and villages.
  • Traffic level: there are high-speed lines carrying 1-2 million passengers a year, and ones carrying 138 million passengers a year (two orders of magnitude!).
  • High-speed line renewal: how long do the different parts of the infrastructure last? (The construction-related CO2 emissions will have to de divided by the total number of passengers over that period.) This is not straightforward. We are speaking of components with a life on the range of decades, and it can both happen that something lasts multiple times longer than originally planned (due to too conservative expectations or advances in maintenance), or that something lasts a fraction of that time (due to bad quality control, unexpected events or corrosive processes, or an upgrade that became a demand or necessity earlier than a regular renewal).
  • Distance: this is a strong factor for air transport CO2 emissions.
  • Airport size and location: air transport related emissions also include some significant construction emissions (runway, terminals, connecting highways and rapid rail) and emissions from airport access transport (which can be anything from a lot of private car driving to a short tram ride).

On the long run, I do think that construction-related CO2 emissions can be reduced significantly. There is research both on the steel and cement front.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Tue Jul 19th, 2011 at 04:39:13 PM EST
[ Parent ]
It doesn't look good if you have to build extensive tunnels or viaducts and pour millions of cubic meters of concrete (with all their attendant CO2 costs). If you strictly want to go for the environmental benefits then you'll want to build higher-speed conventional rail (200-230?). Unless you have a country that's completely flat and empty. The air traffic CO2 problem will resolve itself by curtailment.

Schengen is toast!
by epochepoque on Tue Jul 19th, 2011 at 04:39:30 PM EST
[ Parent ]
you'll want to build higher-speed conventional rail (200-230?)

Well unless it is along an existing line and you'll have lots of trackside buildings to demolish/rebuild and lots of noise walls to construct in villages crossed.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Tue Jul 19th, 2011 at 04:45:46 PM EST
[ Parent ]


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