Electrified modes yield bigger air-quality benefit bang for buck

It would seem that the most efficient transport systems are the most expensive to build. So, there is an obvious trade-off.

Operationally, the most efficient are also the most cost-effective or cost-efficient. That said, at the end of the day, from an operational standpoint, monetarily, the worth of the most cost-effective or efficient should be realized sooner than for those that are less so.

Take, for example, the world’s electrified railway systems. While initially dollar to dollar these are more expensive in terms of their costs of construction, operating costs are usually lower compared with comparably built internal-combustion-driven railways. Operating costs center around purchasing electricity compared to buying diesel locomotive fuel. Both, as it happens, can and do vary.

I looked into this further. From the Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change report, I discovered the “Table 8.1 High-speed rail transport infrastructure GHG emissions based on LCA data” table (p. 618).1

Below is some of what I learned.

Emissions range from 1.0 to 10.9 grams of carbon dioxide equivalent per passenger kilometer (gCO2eq/p-km). The reason for the differences is explained in the corresponding comments section of the table.

For example, for the “Swedish high-speed rail plans for Europabanan infrastructure,” for which an emissions figure of 2.7 gCO2eq/p-km, was indicated, in the comments section was referenced this reality: “At 25 million passengers per year.” For the U.S., meanwhile, which is in the process of building its first high-speed rail line in California, and for which a figure of 3.2 gCO2eq/p-km was indicated, in the comments section the statement “This 725 km line will emit 2.4 MtCO2eq/yr,” was written. (Disclosure: regarding the latter, referenced was a Chang and Kendall, 2011 study). That seems a bit much especially considering that the California system is supposed to be powered by 100 percent renewably-supplied electricity.

However, in the grand scheme of things, maybe not so much after all. So, say the figure for California high-speed rail, at full build-out, which is expected for no sooner than 2029 for the 725-kilometer- or 520-mile-long line connecting Los Angeles/Anaheim with San Francisco, with a state greenhouse gas emissions target of 427 million metric tons of carbon dioxide equivalent emissions output in 2020 (it is at approximately 441 MMTCO2eq right now), a figure of 2.4 million tons of carbon dioxide equivalent emissions per year is a little more than half a percent of all statewide emissions assuming a state output of 427 MMTCO2e in 2029 or 2030 or a slightly higher percentage if in 2030 the state output is less than that estimated for 2020. Either way, in the grand scheme of state greenhouse gas emissions output, the amount projected by California high-speed rail is practically nil.

Further, in the same Climate Change 2014: Mitigation of Climate Change report, the authors write: “Battery electric vehicles (BEVs) emit no tailpipe emissions and have potentially very low fuel-production emissions (when using low-carbon electricity generation). BEVs operate at a drive-train efficiency of around 80 % compared with about 20-35 % for conventional ICE [internal-combustion engine] LDVs [light-duty vehicles].” (pp. 614-615)2

As for carbon emissions of road versus rail, between 1970 and 2010 worldwide, road emissions generated in 1970 were in the neighborhood of 1.6 giga-tons of carbon dioxide equivalent per year (GtCO2e/yr.) and represented 59.85 percent of all emissions generated from transportation. In 2010, such emissions rose to roughly 5 GtCO2e/yr., that representing 72.06 percent of all emissions from transport. (Figure 8.1, p. 606).3

Meanwhile, and conversely, it was shown from the same report, in 1970, rail-based transport emitted about 0.25 GtCO2e/yr. which represented 9.78 percent of all transport emissions, falling to about half that in 2010, amounting to 1.6 percent. (Figure 8.1, p. 606).4

It’s obvious what the differences between the modes picked for comparison and analysis are. Understanding those differences, why the more efficient of the modes or systems in the name of air-quality and human-health benefit isn’t exploited more is puzzling.


  1. Sims R., R. Schaeffer, F. Creutzig, X. Cruz-Núñez, M. D’Agosto, D. Dimitriu, M.J. Figueroa Meza, L. Fulton, S. Kobayashi, O. Lah, A. McKinnon, P. Newman, M. Ouyang, J.J. Schauer, D. Sperling, and G. Tiwari, 2014: Transport. In: Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  2. Ibid
  3. Ibid
  4. Ibid

Image (upper): Charles O’Rear, U.S. National Archives and Records Administration collection

This post was last revised on May 11, 2020 @ 6:53 a.m. Pacific Daylight Time.

– Alan Kandel