|Fig. 1: An image of a Japanese bullet train. (Source: Wikimedia Commons)|
Also known as high-speed railways, bullet trains were first developed in Japan after a ban on their production of airplanes by the U.S. after WWII caused them to further the development of other methods of transportation within their country.  It now serves as one of the fastest and most convenient type of transportation for commuting throughout the nation - reaching speeds of up to 320 km/hr.  Fig. 1 demonstrates what a typical Japanese bullet train looks like. This drastically reduced travel time between major cities in Japan, cutting a seven-hour trip from Tokyo to Osaka to only around two hours.  These trains have been so successful that many other nations in Europe and Asia have followed suit and created their own versions.  While the U.S. has largely shied away from these types of trains in favor of the interstate highway and airlines, we may soon be seeing one of the few bullet trains of America in California. [3,4]
The high-speed rail differs from the traditional rail in many ways; however, we will focus on the few most significant energy-related differences. Firstly, bullet trains distribute their energy over more axles, which lets trains accelerate and decelerate faster because the powered wheels rely on friction between the wheels and rail to transmit power.  Secondly, most bullet trains get electricity from overhead wires or catenaries using a pantograph.  The pantograph collects electrical current from a cable system that runs above the train to the train motors.  And thirdly, these trains have regenerative braking - harnessing the traction motors as brakes to generate electricity - which is sent through the overhead lines to be stored shortly or immediately reused on the line. 
California's very own bullet train may soon be connecting Los Angeles to the Bay Area. Originally scheduled to be fully functioning in 2022, the 220-mph train has been postponed another three years to be released in 2025.  The cost of building the train was initially estimated to be around $68 billion, but new estimates suggest that it could be as low as $64.2 billion.  There have been estimates that the bullet train tickets could cost as little as $50 when first announced on the California bill in 2008 but the state high-speed rail agency has since projected several different fairs since then - the most recent being $86.  This would make it the cheapest high- speed rail on a per-mile basis. 
As promising as this new transportation does sound, there has been a lot of criticism against its production. Some issues are logistical, namely the issue associated with drilling through 36 miles of tunnels through earthquake-prone mountains near LA.  And while a general path has been proposed though California, there are still some concerns about where exactly the path of the rail will cross in areas around the Central Valley that will need to be solved.  Others are more economic in nature, such as whether the rail will make back the money caused to build and run the bullet train or if train tickets must be perpetually subsidized to make them affordable and at competitive prices to alternatives, like driving and airfare.  Similarly, while the construction of the railway should have meant more opportunities for work, particularly regarding the US manufacturing industry, this may have not been the case, with concerns around the California High Speed Rail Authority importing parts and materials from out of the country to save on expenses.  However, the most important concerns that may be had about the California bullet train revolve around energy. 
While high-speed rails depend not on oil, but on electricity, this may not necessarily mean that this form of transportation is any cleaner than its alternatives.  Almost two-thirds of the world's electricity comes from fossil fuels.  Thus, unless power stations separate themselves from fossil fuels, electric trains will still have a significant climate impact - although rail travel is still better than flying or driving.  Similarly, it is unsure whether high-speed rail will draw enough people off the roads and short-haul flights to have a positive environmental impact. 
Moreover, the per-trip energy consumption, greenhouse gas emissions, and other emissions of bullet trains are usually compared against the alternatives (cars, traditional train, and plane), but only considering vehicle operation.  This lacks examining the environmental life-cycle assessment, which looks at both direct and indirect effects of vehicle operation, infrastructure, and fuel components.  Thus, besides looking at the energy consumption and greenhouse gas emissions - SO2, CO, NOX, VOCs, and PM10 emissions were also evaluated by a University of Berkeley study.  The energy and emission intensities of each transportation type were normalized per passenger kilometer traveled by using high and low occupancies to demonstrate the "range in modal environmental performance at potential ridership levels."  They found that while high-speed rail may lower energy consumption and greenhouse gas emissions per trip, it can create more SO2 emissions (given the current electricity mix), which may lead to environmental acidification and human health issues. 
While there are still many obstacles to overcome before the California bullet train becomes a reality, and when it does, transportation in the state may likely change for the better. However, the high-speed rail can only begin to play a major role in tackling climate change in California and around the world if it is truly affordable, powered by cleaner energy and proves itself to be a worthwhile alternative to cars and planes. If this were to finally happen, we may look at these current flaws with the bullet trains as small bumps along the road to a cleaner, faster future.
© Stephanie Tran. 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.
 J. Soble, "Japan, Seeking to Regain Manufacturing Might, Bets on Aerospace," New York Times, 23 Aug 16.
 J. Ryall, "Bullet Train at 50: Rise and Fall of the World's Fastest Train," The Telegraph, 1 Oct 14.
 T. Zoellner, "Making High-Speed Trains Work in the U.S," Wall Street Journal, 31 Jan 14.
 R. Vartabedian, "$68-billion California Bullet Train Project Likely to Overshoot Budget and Deadline Targets," Los Angeles Times, 24 Oct 15.
 S. Koiaumi, "Advance in Railway Vehicle Technology and Future Prospects Mainly in Relation to Bogie," Nippon Steel and Sumitomo Metal Technical Report No. 105, December 2013.
 "High-Performance Pantograph Testing," MTS Systems Corporation, 2010.
 R. Vartabedian and D. Weikel, "Doing the Math on California's Bullet Train Fares," Los Angeles Times, 10 May 15.
 R. Vartabedian, "High-speed Rail Critics Question the First Route Segment, Which Will End in an Almond Orchard," Los Angeles Times, 29 Aug 16.
 R. Vartabedian, "California's Bullet Train Authority Decides to Buy American after All," Los Angeles Times, 18 Nov 16.
 M. Tutton, "How Green Is High-speed Rail?" CNN, 19 Nov 11.
 M. Chester and A. Horvath, "Life-cycle Assessment of High-Speed Rail: The Case of California," Environ. Res. Lett. 5, 014003 (2010).