In the study “Consideration of the ecological and overall social balance of night train transport by rail in an intermodal and intramodal comparison“, the consulting agency Rambøll examined the climate protection potential of an expanded night train network calculated by Back-on-Track on behalf of the Federal Ministry for Digital and Transport.
Our night trains climate saving potential study:
In September 2022, Back-on-Track presented the report “The Global Warming Reduction Potential of Night-Trains” simultaneously to several European transport ministries, including the German Ministry of Transport. Based on data from the IEA and Back-on-Track’s own hypotheses, the voluntary study calculated that, on average, a night train produces 28 times less greenhouse gases than an aeroplane.
Based on data from our French group, the study also calculated the number of air passengers on routes in Europe that could be replaced by night trains and assumed that, under ideal conditions, 69% of air passengers would switch to night trains, as previously determined in surveys. On this basis, the number of passenger kilometres that could be shifted to night trains was calculated. Back-on-Track quantified the climate impact of a consistent expansion of the European night train network with a reduction potential of 3% of the EU’s total GHG emissions, if the necessary political decisions are taken.
The new night trains climate saving potential study:
In the same year, the German Ministry of Transport commissioned a study to determine the ecological and social potential of night trains in a scientific manner. The results were presented on 31 March 2025 in the presence of a small group of selected stakeholders.
While the back-on-track study had examined the maximum potential for Europe, the task of Rambøll’s contract researchers was to investigate the real potential of night trains arriving in Germany, departing from Germany or travelling through Germany, both under existing and improved conditions. In addition, the emissions for the operation of the infrastructure used by the modes of transport and for vehicle construction should also be included. Back-on-track used well-to-wheel data, which takes into account the emissions generated for fuel production and transport, but these do not include the emissions generated for infrastructure and vehicle construction.
Even in 2023, night trains were around 28 times less harmful to the climate than aeroplanes.
However, their inclusion hardly changes the picture. Compared to a well-to-wheel approach, for night trains 21% of total emissions account for infrastructure and vehicles. In air traffic only 2.63 gCO2e/pkm (UBA, p.38), i.e. around 1% must be added. The Rambøll study thus calculates 21 gCO2e/pkm (p. 94) for night trains in Germany. Back-on-Track calculated 14 gCO2e/pkm, albeit for Europe as a whole, based on IEA values from 2019.
At the time of the study (2023), the most recently recorded emissions in the German electricity mix were 329 gCO2/kWh. This is 1.56 times the EU electricity mix of 210 gCO2/kWh. The value of 21 gCO2e for Germany would therefore correspond to around 13.4 gCO2e for Europe as a whole. The 14 gCO2e/kWh we have calculated would therefore already include the emissions for infrastructure and vehicle construction.
Another deviation is the choice of an EWF factor of 2.1 for the calculation of non-CO2 effects. Rambøll decided to work with the “more conservative” values of the Federal Environment Agency from 2020, although the latter had already corrected the factor 2.1 to 4.3 (for 2023). With an EWF approach based on the current state of science, Rambøll would arrive at flight emissions of 388 gCO2/pkm instead of 197.51 CO2e/pkm, similar to Back-on Track, based on fuel consumption in 2019. Taking into account an annual increase in efficiency of around 1.4%, this 368 gCO2e/pkm in 2023 would be 27 1/2 times the correspondingly calculated additional emissions.
Reduction potential: 3% remains a vision, but 0.3% would be feasible.
The overall potential for reducing greenhouse gas emissions, on the other hand, was estimated to be significantly lower than back-on-track. The new study found an additional savings potential of 0.2 Mt CO2e under the given framework conditions. Under optimised framework conditions up to 2.3 Mt CO2e could be saved.
The first step here again would be to replace the outdated EWF factor with the current one. If the share of fuel consumption in flight emissions is multiplied by a factor of 4.3 instead of 2.1, the additional savings potential is 0.4 Mt CO2e and up to 4.4 Mt CO2e if the framework conditions are optimised. Half of this value would be attributable to Germany. This would correspond to a share of the current German GHG emissions of 649 Mt CO2e of 0.03% to 0.3% of annual emissions, even at the upper end only a tenth of the up to 3% that back-on-track promised. This is due to various factors that were actually set more conservatively in the Rambøll study.
Distance limit of 1,500 km halves the overall potential:
The maximum realisable distances were limited to 1,500 km in the study. Back-on-Track also worked with a limit of 1,500 km for conventional night trains, but also considered the potential of high-speed night trains or alternatively multi-day night trains over distances between 1.501 and 2,700 km. This has in our study almost doubled the potential for transferable passenger kilometres.
Current train technology limits the transfer potential to 30%:
Back-on-Track worked with ideal conditions, i.e. new types of night trains that offer an ideal level of comfort, smoothness, privacy, space and safety, depart after 18:00 and arrive before 10:00 and are no more expensive than a flight on the same route. For this reason, our study worked with the entirety of all those who are more likely to switch in order to determine the maximum potential. Rambøll, on the other hand, worked on the assumption of relatively slow night trains of conventional design, predominantly equipped with couchettes, which offer no privacy and limited security. Under these very real conditions, the assumption of a maximum transfer potential of 30% of air passengers is justified. New types of carriages, on the other hand, could justify to unleash the full passenger potential willing to switch to a night train, which is – according to opinion polls – 2.3 times higher.
Incorrect assumptions regarding competitiveness limit the route potential:
Another difference can be explained by the assumptions regarding economic efficiency. The study assumes that night trains are in terms of average ticket prices already competitive with aviation today. It consequently sees no need to improve the regulatory framework for night trains by lowering track access charges and equalising VAT on train and flight tickets. However, the price range of low-cost airlines on which this assumption relies is based on a single snapshot from 2023, which is now outdated. This statement in the study was also most vehemently contradicted by the stakeholders present at the presentation.
Assuming more favourable conditions it would probably be possible to operate a larger proportion of the routes economically. However, without the publication of data on the relevance assessment of potential routes, it is not possible to determine exactly to what extent this factor accounts.
Conclusion:
Applying the current state of scientific knowledge, the study confirms our statement that overnight train journeys are 28 times less harmful to the climate than travelling by plane – even when taking into account the emissions attributable to infrastructure and vehicle construction. With regard to the potential for reducing emissions, the study suggests initially aiming for a realistic emissions reduction of 0.3%, which is achievable with existing network capacities. However, the factors not taken into account in the study provide good reasons to stick to the vision of a 3% reduction in emissions and to demand the necessary improvements.