Speed limit has hardly any noticeable climate effect

A speed limit, which as a result of the war against Ukraine also came into focus as an energy-saving measure, has been the subject of repeated debate for years. In view of the high energy prices and current study results from the Federal Environment Agency (UBA), the topic is now gaining momentum again. The agency has recently come out in favor of a speed limit of 120km per hour on motorways, citing CO₂ savings as the main argument.

But is a general speed limit on motorways really the meaningful contribution to climate-neutral traffic and other challenges that many are hoping for?

In its various studies, the Federal Environment Agency comes to very different conclusions. Noticeable are changes in the methodology and assumptions that seem difficult to understand but have a significant effect on the assumed CO₂ savings, such as modal shift. In addition, the calculations do not take into account that according to the federal government's plans, around a third of the German vehicle population will probably be electrified by 2030 with 15mn electric cars. Due to the current market ramp-up of electromobility, more and more electric cars will of course be registered by then. We are already experiencing this steep market ramp-up of e-mobility today - however, the UBA completely ignores this development in its study.

We see a certain effect on the climate, but doubt the scope presented by the UBA and consider it rather symbolic in the context of the discussion. After all, a general speed limit would have very little impact on climate protection. According to the latest results from the Federal Environment Agency, a speed limit of 120km per hour would save greenhouse gas emissions equivalent to 6.7mn tons of CO₂ equivalents annually - that would be almost 0.9% of the total greenhouse gas emissions in Germany. Compared to global CO₂ emissions in 2021 (36.3bn tons), the share would be just under 0.0186%. However, we expressly consider the value of 6.7mn tons of CO₂ to be far overestimated.

One thing is clear: Motorway sections with an increased risk of accidents, high traffic volumes or construction sites should be subject to a speed limit. But there is no need for a general, rigid speed limit on unobstructed parts of the motorways. The "traffic lights coalition" has also agreed on this.

Federal Transport Minister Volker Wissing also spoke out against government measures such as a general speed limit on German motorways: "Driving pace is the personal responsibility of citizens, as long as others are not endangered. The government should hold back here," Wissing said in an interview with Bild am Sonntag. He calls for better conditions for e-cars and CO₂-neutral fuels in order to promote climate-neutral transport.

And what impact would a general speed limit  have on other challenges such as road safety? We've put the facts together.

More than 96% of German motorways and federal, state and district roads are already subject to a permanent speed limit. 30% of the motorway network has permanent or temporary speed limits. From our point of view, the recommended speed of 130km per hour has proven itself on the non-limited sections.

Instead of general limits, speed limits should be applied precisely via digital control where it makes sense, for example on road sections particularly prone to accidents or in poor weather or traffic conditions.

Motorways are the safest roads in our country. Unfortunately, the risk of dying on a country road is about 3.5 times higher than on a motorway. In addition, safety on German motorways is increasing from year to year: between the years 2000 and 2020 alone, the number of accident fatalities fell by around two thirds. State-of-the-art driver assistance systems in vehicles made a particular contribution to this.

Even in an international comparison, there is no connection between a general speed limit and the level of safety on motorways. In 2018, significantly more traffic fatalities were recorded on the motorways of countries with speed limits such as Belgium, France, Italy or Austria - in relation to the kilometers driven.

A general speed limit on motorways does not contribute to noise protection either: from a heavy traffic share of 10% and above, which applies to over 95% of all motorway sections in Germany, passenger car noise is no longer of relevance. This was the result of a large-scale test on the A 45 near Dortmund.

Rigid speed limits displayed by tin-plate signs, which always indicate the same maximum speed for all traffic and weather conditions, are no longer suitable for a modern 21st century traffic system. That is why Germany should rely on up-to-date digital means such as flexible traffic control systems. Furthermore, the already existing equipment of motorway sections with appropriate variable message signs should be expanded.

In the future, modern driver assist systems will also ensure greater safety. The further digitization of vehicles and infrastructure also creates even better conditions for cruise control related to situation and route.