Agora Review: Dare to Drive Less - Gain More Living Space!

The transportation transformation is changing people's daily lives in different ways. When one of several lanes is reserved for bus traffic, passengers can reach their destination faster and more reliably – but the remaining lanes become more crowded. A residential street without through traffic is safer and more livable for everyone, but drivers look for ways to bypass it. Traffic calming means that shop owners can enjoy more foot traffic and better customer experience in front of their businesses – though some worry about losing customers who previously came by car. In nearby streets, residents wonder if car traffic will now end up right outside their doors.

Such concerns and doubts are understandable, as people have become accustomed to the omnipresence of car traffic over the decades. At the same time, a growing number of well-documented examples show that these concerns are often unfounded. More and more municipalities are reorganizing car traffic and recording the effects through traffic surveys. It becomes clear: Traffic volumes are not unchangeable figures but results of infrastructure planning. People adjust their behavior to the available options: They choose new routes, different modes of transport, or a combination of both, such as Park&Ride.

Traffic Diversion? Many Car Trips Simply Don't Occur

When traffic experiments favor active mobility or public transportation, it is often observed that a significant portion of trips by car identified before the measure do not occur at all. While more road capacity attracts more car traffic, less capacity results in less car traffic. Of course, not all car trips vanish or automatically shift from residential to main streets when space for cars is reduced on a road section. Therefore, traffic calming at the neighborhood level and extensive monitoring are recommended to identify problems and make adjustments if necessary. Practice shows that such changes require courage, but alternatives – building new roads or doing nothing – do not sustainably improve traffic flow, nor do they contribute to climate protection or more livable cities.

Why Car Traffic Decreases Instead of Merely Shifting

It has been known since the 1960s that even with constant traffic volumes, expanding the road network (e.g., by using the side street network on the recommendation of a routing service) can cause longer travel times for all drivers ("Braess's Paradox" from mathematician Dietrich Braess) and that (expansion) of additional roads can cause more traffic in the long term ("induced demand" according to economist Anthony Downs).

This means conversely: Traffic flow is not dependent on the capacity of the entire road network, but primarily on critical points such as individual intersections where traffic volumes regularly exceed capacity.

Therefore, a reduction in the network does not necessarily worsen traffic flow but can even improve it while freeing up space for other uses. According to Down's logic, a lower supply of lanes leads to a reduction in overall demand, meaning fewer cars on the roads.

Traffic Trials: Six Case Studies Under the Microscope

Increasingly, people in civil society and politics are committed to reducing existing privileges of cars in order to decrease vehicle noise, make streets safer for children and the elderly, and motivate people to use bicycles or public transport instead of cars. Many projects also focus on improving the quality of stay, for example in shopping streets or residential areas, or on climate-resilient redesign to better absorb rainwater and mitigate heat islands in the summer. To temporarily test such traffic-calming or -regulating measures, the traffic regulations have simplified the use of the "experimentation clause" since the 2020 amendment (§ 45 para. 1 sentence 2 StVO). Since then, so-called traffic trials no longer require extensive justification of significantly increased danger, thereby reducing administrative effort. As a result, numerous cities have now made use of this trial clause, and internationally, there are more and more insights into the impacts of traffic trials. Some examples are presented below.

Basically, the following types of trials can be distinguished: Conversion of lanes, for example into a bus lane (example Potsdam) or a bike lane (example Bremen), traffic calming in residential areas through entry/through-traffic restrictions (examples Berlin, England, Bremen, Hamburg), and the complete repurposing of streets, for instance into pedestrian zones (example Munich).

Berlin: Promenade Friedrichstraße

One of the most prominent examples of recent times is Berlin's Friedrichstraße. Converted into a so-called promenade (with a bike lane) since August 2020, the project has been widely discussed in the media. While some aspects of the temporary redesign are certainly debatable, the interim evaluation of the trial paints a positive picture. Half of all respondents said that they felt the traffic calming was a reason to visit Friedrichstraße more often. Over 80 percent also expressed support for a permanently car-free street as well as similar projects in Berlin.

While pedestrian traffic on the promenade increased by up to 50 percent in some months, vehicle traffic partly shifted to surrounding streets. However, this did not lead to an overload there. Only the parallel Charlottenstraße recorded a significant increase in traffic, which affected traffic flow there. The other streets were also used as alternative routes, but were able to absorb the additional traffic volume without any problems due to their network classification as "neighborhood street" and street layout.

A good third of the car traffic that previously passed through Friedrichstraße disappeared entirely from the area during the trial period. Of the former 36,400 daily vehicle trips on Friedrichstraße, only 23,600 additional trips were recorded on the parallel streets.

This shows that people adapt their routines and decisions by bypassing the area more broadly by car or choosing other means of transportation. Nonetheless, the (albeit partial) shift created new burdens on the surrounding streets – which likely also contributed to a complaint from a business owner located on Charlottenstraße. Meanwhile, it has been decided to fully convert Friedrichstraße into a pedestrian zone and reroute bicycle traffic via Charlottenstraße, but the necessary partial road closure has not yet been completed. Since the traffic trial is officially considered over, cars will return to Friedrichstraße for the time being until the final repurposing is completed, following the decision of the Berlin Administrative Court.

Munich: Pedestrian Zone Sendlinger Straße

In Munich, the northern section of Sendlinger Straße was converted into a pedestrian zone some time ago. Following the success of this first step, the southern area was also traffic-calmed and urbanistically redesigned on a trial basis. The city of Munich placed great emphasis on extensive participation opportunities and a comprehensive evaluation of the effectiveness of the measures. Traffic surveys before and during the trial suggested that weekday traffic volumes hardly changed, so the traffic burden on the surrounding neighborhood remained almost the same. On weekends, traffic increased slightly during peak times, but did not exceed the capacity of the surrounding road network and was overall lower than the total weekday burden. The evaluation report therefore classifies the changes as "transportation planning defensible." The repurposing gave pedestrians significantly more space, allowing more people to use the area.

Sendlinger Straße is therefore a good example of how the creation of a pedestrian zone can improve the quality of life and positively impact local retail, especially in shopping streets.

Bremen: Experience Space Martinistraße

While Sendlinger Straße in Munich was initially conceived as a pedestrian zone, the planning orientation in Bremen's old town under the designation "Real Laboratory for the Future City" was initially much more open. Between July 2021 and April 2022, three different traffic trials were conducted on the formerly four-lane Martinistraße, accompanied by various activities (e.g., installations, concerts, film screenings, street theater).

The project began in the first phase with a full closure of Martinistraße to vehicle traffic, creating a particularly large open space used for events during the holiday season, and also linked to the construction site-related closure of the intersection. In the second phase, lanes were removed and a one-way street for vehicle traffic was designated to reclaim as much space as possible in the side areas for other uses. In the third and final phase, vehicle traffic was reduced to one lane per direction and additionally protected bike lanes were created. All three phases were scientifically monitored and evaluated.

The evaluation shows that particularly in the third phase, traffic changed significantly. Vehicle traffic in the old town and surrounding area decreased by at least 15 percent at more than half of all 30 counting points.

A (moderate) increase in vehicle traffic was recorded at only four counting points, which did not result in overload. The even utilization of a nearby parking garage during the three trial phases also demonstrates that motorists continue to reach the city center. This leads to the conclusion that only through traffic was diverted to wider alternative routes by the measures in the third phase, or some people refrained from driving their car. Based on the evaluation of the results, it was suggested that the currently established phase of "one-lane two-way traffic with protected bike lanes" be fundamentally maintained and further optimized.

Hamburg: Ottensen Makes Space

The "Ottensen Makes Space" project in Hamburg's Altona district also temporarily converted the Gründerzeit-era center into a car-free "promenade quarter." From September 2019, parking in the street and entry into the project area were largely prohibited. A total of 800 meters of street was designated as a pedestrian zone and various seating and planting elements were installed in the public space. The trial received broad approval. Around 78 percent of the surveyed passersby rated the trial as good or very good for the district. In Hamburg-Ottensen, too, some motorized traffic shifted to surrounding streets – but without overloading them, as the intended capacities remained significantly undershot. For example, one side street (Kleine Rainstraße) recorded 10 to 50 percent additional traffic volume depending on the day of the week. However, the total vehicle volume there remained so low that the capacity limit was not exceeded and it did not result in significant additional burdens for residents. On the other hand, Bahnefelder Straße, leading into the project area, recorded around 80 percent less vehicle traffic.

This results in an overall reduction in traffic volume in the project area by around 15 to 25 percent. This proportion of former traffic either bypasses more broadly or disappears completely.

Following the evaluation of the traffic trial, a new concept was developed involving citizen participation, which now permanently plans to "close the central area of the project zone to general vehicle traffic." Traffic in the surrounding area is to be further calmed with the help of the establishment of bike streets and retractable bollards to prevent displacement effects.