Carbon Footprint of a High-Speed Train

In 2009, Mikhail Chester and Arpad Horvath of Berkeley’s Institute for Transportation Studies published a paper entitled “Life-cycle assessment of high-speed rail: the case of California” in the academic journal Environmental Research Letters. The paper suggested high-speed trains were not so green, with possibly negative cost/benefit.

The paper went viral, particularly among Libertarian types, even though there were huge blunders in the study. One error was the unrealistic seat occupancy numbers (as low as 10%). But even worse was a units-conversion error, as discovered by Clem Tillier:

Berkeley’s numbers are undone by a simple unit conversion error committed by a CHSRA consultant. Conversions between metric and imperial units are prone to errors and misunderstandings, most famously in the case of NASA’s $300 million Mars Climate Orbiter mission, which was inadvertently crashed into Mars because of an overlooked conversion between pounds and Newtons. In the case of the high-speed rail study, the CHSRA consultant’s unit conversion error leads to an overestimate of HSR energy consumption by a factor of nearly four–not just in the Berkeley study, but also in the CHSRA’s program level environmental reports.

The energy consumption figure cited in the Berkeley study and its supplementary data is 170 kilowatt-hours per vehicle kilometer traveled, or kWh/VKT, a measure of how much energy a high-speed train consumes on average when traveling one kilometer. This number is correctly converted by Berkeley from a figure of 924,384 BTU/VMT referenced in the energy chapter of the 2008 CHSRA program-level EIR. That chapter in turn references a peer-review study performed for CHSRA by the German firm DE-Consult in 2000, which evaluated the energy consumption of a hypothetical 16-car trainset with a seating capacity of 1200 and a design speed of 385 km/h (240 mph) and an operating speed of 350 km/h (220 mph), essentially a souped-up German ICE3. The DE-Consult study (unavailable online) contains detailed performance simulations for the proposed California system that give the average energy consumption of such a train as 74.2 kWh/VMT, or 46 kWh/VKT (see copy of Annex 4-11). And therein lies the error: CHSRA’s consultant botched the conversion from kilowatt-hours to British Thermal Units, feeding Berkeley a figure of 170 kWh/VKT instead of 46 kWh/VKT.