The topic is a "perennial issue" in transport policy and is often discussed emotionally. We are talking about the speed limit on German motorways. It will remain a relevant and much-discussed topic in the 2021 federal election year, as it is included in many election manifestos. And only at the end of April, the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety published the results of a representative population survey on environmental awareness in Germany in 2020. One result of the study is that 64 percent of those surveyed are in favour of introducing a general speed limit on motorways.

"Interestingly, despite this constant topicality, there are hardly any scientific publications on this subject, especially for Germany," says Dr. Andy Obermeyer, member of staff at the Chair of Economics, esp. Transport Policy and Spatial Economics at the "Friedrich List" Faculty of Transport and Traffic Sciences. He and his colleague Dr. Stefan Tscharaktschiew have dealt with the topic of "speed limits on motorways" in more detail from a scientific perspective in recent months.

The starting point was a scientific paper by Stefan Tscharaktschiew, which was published in "Science Direct" in August 2020:

"Why are highway speed limits really justified? An equilibrium speed choice analysis"

Important points in it include:

• Speed externalities are commonly cited to justify highway speed limits, but they could already be internalised if there were an existing policy related to speed.
• In Germany, where fuel taxes are relatively high, the externalities of speed are largely internalised and the externalities argument in favour of speed regulation does not apply to the majority of drivers.
• Nevertheless, a moderate speed limit of 130 km/h on German motorways would probably not affect economic efficiency, at least as long as the share of diesel vehicles is significant.
• Lack of rationality always justifies speed regulation, unless suitable "nudges" (i.e. a "soft" influence to change behaviour) are available.

Based on their research, Stefan Tscharaktschiew and Andy Obermeyer had also written a commentary on the speed limit for die magazine "Wirtschaftsdienst" last year. In it, they emphasise the importance of a holistic view in which the various effects of a speed limit must be weighed against each other. It is an open access article that can be downloaded as a PDF from Springer publishing house.