Recently, I’ve been averaging about 6000km by rail a month and have been reflecting on my levels of carbon emissions. One of my longest journeys took me from Geneva through Bern, Basel, and Frankfurt to reach Berlin on an overnight journey.
While I was pondering on how much carbon I emitted to the environment, I came across two issues with the calculation of my emissions. The first is the composition of the source of energy (nuclear, coal, solar) for trains in different countries, and the second is the actual direct impact on the reason for emission (i.e. a train will run even if you don’t ride it). For the purposes of this article, we’ll only consider non-renewable sources as “carbon emitting” even though renewable sources also have their environmental impact.
On the first issue, a documentary by Rick Steves in the early 2010’s on great train journeys in Switzerland interviewed a SBB engineer who said that 86% of the power provided to Swiss trains were from renewable sources. Now, that number is near 90% hydroelectric power dedicated to powering Switzerland’s railway system according to the SBB’s website. For Germany’s DB, 57% of all traction energy came from environmentally-friendly sources as of 2019. However, those using a BahnCard or seasonal subscription service to travel do so with 100% renewable energy. How they separate trips between subscribers and non-subscribers can only be explained by German math wizards, but we’ll assume it’s true anyways.
With those facts in mind, calculating the exact carbon emissions of an international train journey is no easy feat. First, you’d have to figure out how much each country’s railways emits per kilometer and how many kilometers you travel in each country. Then, you have to figure out what kind of subscription you have in each country to find out what the actual rate of emissions are. Confusing, right? But then consider the second issue: if you didn’t board that train, it would still have run anyways. So how much carbon are you really emitting?
While the second question is much harder to answer and I am underqualified to formulate an answer to it, we can take a look at it from several factors. Public transportation has a different dynamic when compared to individual transport like cars or ride shares, as they run according to schedule. If you travel during a normal or a non-peak period, e.g. a Saturday afternoon, then it could be reasonable to say that you’re not actually causing any carbon emissions because the train would have run to schedule regardless of if you were on the train.
Public transportation companies generally have a minimum schedule requirement to meet even if there is low demand on a line to provide for public access to the disabled, seniors, and children. So even if lots of people decide not to go out on a Saturday, there may not be a reduction in frequency. If frequency becomes too low, public transport becomes inconvenient and people will start using cars, defeating the whole purpose of reducing carbon emissions.
According to this logic (if it is correct), then the only time any individual passenger would lead to an direct causation of carbon emissions is if they are a part of a peak hour group of commuters where operators respond with using additional vehicles or carriages. If one major company in an area decided to let its workers off on flexible times would that lower peak demand and reduce the number of departures for a particular hour? If so, then those people, if not on flexible time would trigger additional emissions. But even then, the average emission per person would be low because the peak-hour vehicle would be packed with passengers.
From a distance perspective, it can be possible to calculate individual emissions based on average capacity, but from a scheduling perspective it’s impossible to know exactly how much emissions are caused individually.
