The LA Subway Blog

Juan's note: I'm crossposting this from my new blog: www.localclimateaction.com

Because I was unsure of the findings, I spent some time looking at the Booz Allen Hamilton/Department for Transport High Speed Rail Study (Estimated Carbon Impact of a New North-South Line) mentioned in a Freakonomics Blog Post.

First, I went to look at the source documents. This was a bit difficult, because footnote xii is actually a link to the AEA study source document. None of the links on footnote x, which is supposedly the AEA study, lead to any usable data for this study.

Looking at the AEA study for DfT, I'm able to see how they got the AEA figures. 49 for average passenger rail, 109 for all cars, 76 for bus, 180 for plane. However, they leave out the Class 373 EMU(high speed rail train).

I was unsuccessful in searching for the June 2007 DEFRA statistics released in the study, but I did find the updated 2009 statistics. Each year, DEFRA (UK's EPA) publishes statistics that they have businesses use to calculate their scope 3 (indirect) emissions from rail travel. This study shows a figure of 17 g/pkm for Eurostar, specifically the high speed rail route between London and Paris. This figure could be a bit low, because France derives a high proportion of their energy from a non-ghg-emitting source (nuclear).

Looking at the Center for Neighborhood Technology study's figure for the Danish IC3 Diesel Multiple-Train Unit and converting lb/pmi to g/pkm, I get 72.71, which is the same (73 g/pkm) as the study.However, the IC3 is diesel-powered conventional rail train capable of a top service speed of 112 mph, not a high speed rail train. Better comparables would be the ICE line 6 in Germany or the TGV in France, which have lower g/pkm emissions.

At this point I was left wondering if the report's authors meant to analyze the impact of a mid-speed diesel powered train line instead of a high speed line. Although the report was light on specifics, the authors did mention that they meant to analyze the effects of efficiency gains in "traction electricity," although this may refer to maglev. They could have also assumed much lower load factors for these routes, although they did not state this in their assumptions.

Needless to say, I'm convinced that the study is flawed.

However, assuming it is not flawed, the energy mix still differs from region to region (different power pools have different generation and emissions profiles). I found the UK-wide electricity emissions-factor on DEFRA's site, which is 546.67 kG of CO2 per mWh. Using the EPA's eGRID data for the California region, I converted lbs/kWh to 398.57 kG of CO2 per mWh. So, California's electricity results in about 73% of the emissions in the UK, per unit of delivered electricity.

So, even if the report was correct, and high speed rail emissions in the UK would emit 88 g/pkm (which I highly doubt), the equivalent technology would only emit 64 g/pkm operating in California.