Sustainable Transportation Energy Pathways (STEPS)
Isaac, Raphael and Lewis Fulton (2017) Propulsion Systems for 21st Century Rail. Transportation Research Procedia 00 (2017)
This paper evaluates the practicality, costs and greenhouse gas-related benefits of different propulsion technologies and fuels for U.S. freight and passenger (i.e. intercity/commuter) rail. Two example routes, one existing (for passenger rail) and one devised (for freight), are used to construct the analysis and better understand the implications of fuel strategies in a “real world” context.
Although diesel-electric locomotives currently dominate freight and non-urban passenger rail, a number of other fuels could be considered in the near future. These include biodiesel and the new “renewable diesel” drop-in diesel replacement fuels. With the low prices of natural gas in recent years, it is another important fuel alternative. Though few longer-distance rail systems in the US run on electricity, this energy carrier is widely used in Europe. Finally, hydrogen and fuel cells are now being explored for non-urban rail systems and some rail yard applications. These options and the requisite locomotive technologies are all considered for our example routes.
Our two scenarios include a passenger rail analysis based on California’s Amtrak-Capitol Corridor line, and a freight analysis based on a generalized 2000-mile (3,218.7 km) corridor. These allow us to size and cost out the locomotive and refuelling infrastructure needed in each context. We find that costs and CO2 impacts of the technology/fuel options vary depending on these applications, particularly due to the much more energy- and fuel-intensive nature of freight rail; however all of the fuel options could, in principle, serve long-distance rail systems, though potentially involving some refuelling system compromises. For both submodes there are several alternatives to diesel that provide CO2e reductions and some that provide cost savings, but no options that are clear winners in both respects.
Keywords: passenger rail; freight rail; alternative fuels; intercity rail