Clean Transport Zones: How to Check if Your City Needs Them?

Clean Transport Zones (CTZs) or Low Emission Zones (LEZs) are currently one of the main topics in the debate on urban policy, as they affect the daily lives of drivers – from commuting to work and school to using services and the logistics of local businesses. They stir up emotions, spark debates, and often become a source of conflict between residents, local authorities, and the media. Emotions are natural – but for local governments, the stakes are higher than transport policy alone.

However, it is worth emphasizing that the assessment of CTZs cannot be reduced to a simple division into “good” or “bad.” The key point is that their effectiveness and public acceptance depend on the quality of the evidence on which they were introduced.

CTZ is not a “dispute over cars.” It is a test of the credibility of local governments

CTZs have now become a test of the quality of public decisions. 

If a city introduces restrictions without evidence, residents hear: “someone came up with it because it has to be done.” If the city shows data before the change, goals, and data after the change, residents see: “the authorities are acting responsibly.” 

Introducing Clean Transport Zones without solid local data is a political, reputational, and operational risk. On the other hand, evidence-based measures become a tool that allows the city to defend its decisions and build trust among residents.

CTZ is a solution that can make everyday life challenging 

The introduction of CTZ is a tangible change that affects everyday life for all residents. The implementation of the zone means:

• restrictions on entry for some vehicles
• changes in the daily mobility of residents and traffic flow
• the need for both individual drivers and businesses to change their routes and habits
• additional costs associated with adapting to the new rules.

This makes CTZs a tool with a high risk of social conflict – especially if residents do not see a clear, documented problem that the zone is intended to solve.

Residents expect evidence, not declarations. Narratives such as “other cities do it” do not build support. What does build support is transparent, local data that shows the scale of the problem, explains why this particular intervention is needed, and reduces the risk of protests and resistance.

2030 is getting closer. CTZ without data could harm cities

European Union member states are preparing to tighten air quality standards by 2030, bringing them closer to the WHO’s strict recommendations. This is a key element of the EU’s “zero pollution” strategy, which aims to achieve pollution neutrality by 2050.

For cities, this means one thing: much greater responsibility for demonstrating that the measures taken are truly commensurate with the scale of the problem and lead to a lasting improvement in air quality.

And here is the key difference: environmental law and targets say “improve air quality.” They do not say “introduce CTZ.”

CTZ is a tool. And tools are chosen according to the scale and nature of the problem.

In many European cities, CTZs continue to cause controversy, not because they were a bad idea, but because there was a lack of local measurements and a reliable diagnosis of the problem. We can find such zones in cities like Berlin, Munich, Paris, Milan, Rome, Amsterdam, Brussels, and London.

An example of the scale of the discussion is Kraków, where the Clean Transport Zone came into force on January 1, 2026. Its introduction sparked a wide public debate, media interest, and numerous questions from residents about the rules, exceptions, and the purpose of the regulation.

The lack of solid data when implementing CTZ can result in intense discussions, political pressure and, in extreme cases, the need to withdraw or significantly revise decisions, which undermines the credibility of the city. It is a reputational, legal, and operational risk.

In an era of growing social and political pressure, cities cannot afford to implement CTZs based on guesswork.

London shows how data can keep policy standing in the heat of criticism

For years, London has consistently linked transport policy to public health and NO2 levels. In its CTZ reports, the city presents, among other things, improvements in air quality and decreases in NO2 concentrations at most monitoring points.

This is important not because “London is right,” but because there is a simple rule in public debate: controversial regulations can only be defended if they are based on measurable effects.

Data changes the dynamics of the dispute – it shifts the conversation from “does this make sense?” to “how can we improve this tool?”

CTZ based on evidence – a tool for defending the city’s decisions

The most criticism-resistant CTZ implementations do not start with prohibitions. They start with analysis. Solid data enables the city to justify its decisions and clearly demonstrate why the Clean Transport Zone is necessary. It forms the foundation on which arguments, communication, and implementation plans can be built. Without it, every decision becomes vulnerable to criticism, but with it, decisions gain credibility and resistance to social pressure.

In practice, obtaining data means:

• local air quality measurements (from fixed and mobile stations)
• analysis of emission source
• modeling the impact of traffic on pollutant concentrations.

With this information, local governments can make decisions based on facts rather than intuition. The data allows them to:

• determine where CTZ makes sense and where it does not, as it indicates which areas actually require intervention
• select zone boundaries so that they correspond to the actual problem, rather than arbitrary assumptions
• plan implementation stages, taking into account local conditions and residents’ needs
• assess effectiveness after launch by comparing the “before” and “after” situations based on precise indicators.

In this way, the city can clearly identify where the problem lies, what its scale is, and what benefits the introduction of a Clean Transport Zone can bring.

How to prove the need for a CTZ in practice? Check whether your city actually needs it

Before a city decides to introduce a Clean Transport Zone, it is necessary to check whether there are solid grounds for doing so. CTZ is a tool with a significant social impact, so each stage of preparation should be based on facts. The first step is diagnosis – understanding what the initial situation looks like and whether transport is indeed a key problem for air quality.

A network of low-cost sensors, which complement the reference stations, plays a key role in this process. Thanks to them, the city is able to conduct measurements in a much larger number of locations. Such sensors allow real-time observation of concentration variability, identification of local pollution hotspots, and precise comparison of the situation before and after the introduction of regulations. Hyperlocality and data continuity enable a reliable assessment of whether transport is indeed the main source of the problem and whether CTZ is an adequate tool for the scale of the challenge.

The next step is to gather evidence that builds credibility and allows for responsible decision-making. This is not a one-time activity, but a process that creates a solid foundation for any regulation.

The zone should be designed based on precise data: where exceedances occur, at what times, and under what weather conditions. It is equally important to constantly monitor its effects – taking regular measurements, comparing the results with the period before implementation, and conducting ongoing evaluation, which allows for the correction of assumptions and optimization of the SCT’s functioning.

CTZs only work when based on reliable evidence

Cities cannot afford to implement Clean Transport Zones based on trends, pressure, or intuition. It is one of the most socially sensitive tools of urban policy – if poorly designed, it can cause opposition, polarization, and a loss of trust among residents.

A Clean Transport Zone implemented without reliable, hyperlocal data quickly becomes a burden: political, reputational, and operational. However, when implemented on the basis of evidence, it becomes a shield that allows decisions to be defended, their meaning explained, and their effectiveness proven.

It is therefore essential that any decision regarding CTZ must be based on an analysis of local data that clearly shows where the problem lies and why intervention is necessary. Without this, the zone will not only fail to work, but may harm the city more than it helps it.