|
|
| Fig. 1: The Tohoku Shinkansan is one of Japan's bullet trains. In the image we can see the long beak shape design at the front of the train intended to minimize resistance as the train reaches speeds up to 320 km/hr. Wikimedia Commons) |
High speed rail systems (> 250 km/hr) are among the most energy efficient forms of long-distance transportation. Their performance is shaped by physical forces such as aerodynamic drag, rolling resistance, and braking energy recovery. This project examines how these factors determine energy use, compares high speed rail to air travel and cars, and evaluates why high speed rail can achieve lower energy per passenger mile.
At high speeds, aerodynamic drag becomes the dominant force opposing motion. Drag grows with the square of velocity, which means small increases in speed lead to much larger increases in required power. In fact, at 300 km/hr, drag accounts for 85% of the total resistance. [1] As a result, engineers made the trains to have very long, front beaks as shown in Fig 1. This reduces air resistance and allows for sustainable high speeds.
Additionally, in Japan, a new magnetic levitation bullet train is now under construction. Using electrodynamic suspension to prop up the train and superconducting coils which "pull from the front and push from the back" this new maglev train will reach speeds of 500 km/hr. [2]
Rail is the least emissions-intensive mode of passenger transport. In fact, according to Jason Karpman of UCLA, "HSR (High Speed Rail) emits 66 to 97% less GHG (green house gas) emissions per PKT (per passenger-kilometer traveled) than flying (not including embodied emissions from construction)". [3] However, one study predicted that building California's 520-mile line would release 9.7 million metric tons of greenhouse gases, or 18,650 tons per mile. [4] With these numbers in mind it could take more than 70 years to repay the construction cost and this is ignoring maintenance repair costs.
On the energy side of things, rail is slightly more efficient than cars and planes. The French TGV and German ICE (both high speed rails) operate at 0.2 MJ per passenger-km which is more than 5 times more efficient than both planes and cars. [5]
High speed rail has seen success around the world specifically in Asia and parts of Europe. While energy and emission intensive to construct, there is promise for train usage to be efficient in comparison to automobile and airplane travel.
© Kush Arora. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] M. Yang et al., "Moving Model Test of High-Seed Train Aerodynamic Drag Based on Stagnation Pressure Measurements," PLOS One 12, e0169471 (2017).
[2] K. Kotaka, "Chuo Shinkansen - a High Speed Japanesse 'Maglev' Train," Physics 240, Stanford University, Fall 2025
[3] J. Karpman, "Brace for Impact: The Environmental and Economic Effects of ShiftingPassenger Travel From Airplances to Hign-Speen Rail," UCLA Institute of Transportation Studies, UC-ITS-20221-52, January 2022.
[4] R. O'Toole, "The High-Speed Rail Money Sink," CATO Institute, April 2021
[5] V. Smil, "Fast Trains Are Energy Efficient," IEEE Spectrum, 26 Dec 18
.jpeg){kind=link}