What does the speed limit report say?
fAlmost seven million tons of carbon dioxide (CO2) save – just like that? Only with one speed limit of 120 kilometers per hour on motorways? According to a study by the Federal Environment Agency from January. New demands for a speed limit were promptly raised, especially since German traffic is not meeting its emission targets. The FDP, from whose ranks Transport Minister Wissing comes, did not want to let that stand.
For its part, the parliamentary group has commissioned a short study that raises concerns about the study by the Federal Office. She also does not deny that a speed limit would save emissions. But she questions whether this reduction is significant and even efficient. The authors of the study, transport economists Alexander Eisenkopf and Andreas Knorr, consider the value calculated by the Federal Office to be excessive. According to their estimate, a speed limit could at most 1.1 million tons of CO2 save on.
For the Federal Environment Agency (UBA), a team of traffic scientists from the Universities of Stuttgart and Graz and employees of a consulting company wrote a report between 2019 and 2022 in which they examined seven different measures against climate change and air pollution. A good month after publication, the FDP experts followed suit. The authors of both studies sit on the Scientific Advisory Board of the Federal Ministry of Transport.
How come the results are so different? This also has to do with the picture the experts get of what is happening on the Autobahn. Every report has assumptions that are convincing and those that are less obvious.
Different assumptions
The biggest difference: The study by the Federal Environment Agency not only estimates how much emissions cars save on the motorway in the event of a speed limit. The authors also argue that some motorists would then choose other routes, for example shorter ones on federal highways in terms of kilometers. In addition, some car journeys would be replaced by other means of transport or would be eliminated altogether. The authors of the FDP study consider the calculation of those effects to be speculative and therefore limit themselves to the direct speed effect.
In addition, the FDP experts also doubt the calculations of the speed savings. The UBA authors are working with data from 2018. In the meantime, the corona pandemic and high fuel prices have ensured that people get into their cars less often and drive more slowly – as shown by several data sources, only users of Tomtom devices seem to disagree to behave. The speeds actually driven have therefore reduced, and with it the possible savings potential.
Then there is the question of how fast drivers would actually be driving if there was a speed limit. In the UBA study, the authors assume that people with a nationwide speed limit drive as fast as on the routes where a maximum speed of 120 currently applies. But today’s speed limits have a reason, because cars usually can’t drive too fast on these routes anyway, for example because of curves or poor road surfaces. Routes that currently have no speed limit, on the other hand, tend to invite you to drive at high speeds, so that people would drive faster here on average even if there was a speed limit.
Wrong choice of cars for the study?
On the other hand, the FDP experts seem to be wrong with the accusation that the UBA primarily analyzed the speeds of expensive cars. The UBA authors have included the data for expensive cars tom-tom Bought and used but not used directly to estimate speed. There is also a dispute as to whether they underestimate the fuel savings at lower speeds. Both studies have their question marks.
The actual emission savings from driving slowly are therefore between the two values of the reports, probably between two and four million tons per year. Whether it’s exactly two or four is perhaps not so important. Even this fuzzy value can be easily compared. Two to four million tons seems negligible when compared to other measures.
For example, with the continued operation of the German nuclear power plants, which would have saved emissions by 50 million tons a year. The FDP experts come to the conclusion that every tonne of CO2 costs around 390 euros – climate protection is cheaper elsewhere, European CO2-Emission permits currently only cost 80 euros. On the other hand, the Climate Protection Act has set sector-specific emission targets that the Ministry of Transport missed by 3 million tons in 2021. A speed limit would have saved Minister Wissing some debates about climate protection measures.
In a few years, however, the discussion about a speed limit could become obsolete anyway. That is when the transport sector is included in public emissions trading at the end of the decade. At this moment there is an emissions cap for traffic that will definitely be reached.
