Major cities worldwide increasingly adopt Low-Emission Zones (LEZs) and Zero-Emission Zones (ZEZs) as critical tools to combat persistent urban air pollution and manage traffic congestion.
These progressive policies mark a significant and evolving global trend in urban environmental policy. It moves from reactive measures to meeting air quality standards to more proactive strategies focused on broader climate goals and reshaping urban life.
From low emissions to zero tailpipe
At their core, LEZs are geographically defined areas where access for vehicles emitting high levels of harmful pollutants is restricted or subject to a charge.
Their primary objective is to improve local air quality by discouraging using older, dirtier vehicles. It aims to reduce pollutants like Nitrogen Oxide (NOx) and Particulate Matter (PM), which are known to harm public health.
Many European cities initially implemented LEZs, often known as Clean Air Zones (CAZs) or Zones à Faibles Émissions (ZFEs), to comply with national or European Union air quality directives.
Access is typically managed by setting minimum emission standards, often based on “Euro” classifications or national systems like France’s Crit’Air vignettes, banning non-compliant vehicles or requiring them to pay a daily fee.
Zero-emission zones (ZEZs) represent a more stringent evolution of this concept. Within ZEZs, only vehicles with zero tailpipe emissions, such as battery electric vehicles (BEVs) and hydrogen fuel cell vehicles (FCEVs), alongside non-motorized transport, can access the area.
ZEZs’ goals are more ambitious. They aim to eliminate tailpipe emissions, contributing directly to urban decarbonization and climate neutrality.
They are also designed to significantly accelerate the adoption of zero-emission vehicles (ZEVs) and encourage a fundamental shift from private car dependency towards sustainable transport modes.
It is crucial to distinguish these zones from congestion charge zones, which primarily target traffic volume and revenue generation, though they may offer secondary air quality benefits.
Furthermore, recognizing the significant impact of commercial vehicles, some cities are pioneering Zero Emission Zones specifically for freight (ZEZ-F), tailoring policies to the unique challenges of urban logistics.
The intensity of these policies varies widely, reflecting different local priorities, political landscapes, ZEV market maturity, and public acceptance levels.
The global phenomenon of national and city action
Implementing LEZs and ZEZs has accelerated dramatically, particularly in Europe, and is gaining momentum in other regions.
The European Union and Great Britain lead the way, with over 320 active LEZs as of 2022, projected to exceed 500 by 2025. Stringent EU air quality standards and increasing public pressure heavily influence this growth.
Several EU member states have established national frameworks acting as catalysts. The Netherlands, for instance, mandates ZEZ-Fs in 30 to 40 of its largest cities by 2025, supporting this with subsidies and charging infrastructure. France’s Climate and Resilience Law requires LEZs (ZFEs) in all urban areas with over 150,000 inhabitants by 2025, using the progressive Crit’Air system.
Similarly, Spain’s 2021 law mandated LEZs (ZBEs) in municipalities with over 50,000 inhabitants by 2023.
The UK has prompted cities to establish Clean Air Zones through a national framework, with London’s expansive Ultra Low Emission Zone (ULEZ) being a prime example.
Alongside national directives, international city networks like the C40 Cities Climate Leadership Group are influential. C40’s Green and Healthy Streets Declaration commits over 36 cities, including Paris, London, Los Angeles, and Amsterdam, to establish significant zero-emission areas by 2030.
These networks facilitate knowledge exchange and peer learning, supporting cities even without strong national mandates.
Momentum is also building beyond Europe. Shenzhen, China, is recognized for its “Green Logistics Zones,” a form of ZEZ-F that showcases a commitment to electrifying urban freight. Seoul, South Korea, has implemented LEZs.
In North America, pilot programs such as Santa Monica, California’s voluntary Zero Emission Delivery Zone (ZEDZ) pilot, and Los Angeles’s plans for ZEAs and ZED curb zones are emerging.
Latin America is also showing interest, with Guadalajara, Mexico, announcing an LEZ, and several major cities like Bogota, Medellin, and Santiago being C40 signatories. Kevadia and Ahmedabad in India also present examples of LEZ interest or implementation.
A common thread in these initiatives is a phased implementation strategy, gradually tightening restrictions or expanding coverage over time. This approach allows residents and businesses time to adapt and authorities to develop necessary infrastructure and enforcement systems.
Tangible benefits and impacts
The growing evidence base confirms that LEZs and ZEZs deliver significant air quality improvements. London’s ULEZ has shown substantial success, with roadside NO2 concentrations 27% lower across London and 54% lower in Central London than they would have been without the zone and its expansions.
NOx and PM2.5 exhaust emissions from cars and vans in outer London also saw significant decreases post-expansion. Cumulatively, NOx emissions across London are estimated to be 24% lower, and PM2.5 exhaust emissions 29% lower from 2019 to 2024 due to all ULEZ phases.
In Paris, projections for the ZFE-m indicated reductions in NOx, PM10, and PM2.5, and reports from Airparif have generally shown decreasing trends in NO2 and PM concentrations. Barcelona’s ZBE achieved the lowest NO2 levels in 25 years in 2023. Madrid’s ZBE is estimated to have reduced NO2 by 29% to 35% in 2022 compared to a no-LEZ scenario.
A review covering various European cities found an average NO2 reduction of around 20% in LEZs, with specific examples like Brussels seeing a 33% reduction and Lisbon a 22% reduction.
Substantial motor traffic reduction
The impact on traffic dynamics is more complex. While zones alter the vehicle fleet composition within their boundaries, their effect on total traffic volume and congestion can vary.
London’s ULEZ expansion reportedly had no significant adverse impact on overall traffic volumes or economic activity, with high vehicle compliance rates. However, some studies suggest potential traffic displacement to surrounding areas. Madrid’s LEZ initially reduced traffic flow within the zone but saw some displacement and a subsequent rebound in traffic as the fleet renewed.
LEZs and ZEZs intend to encourage a shift towards sustainable modes of transport. London’s policies have reportedly encouraged such a modal shift. Evidence from Madrid also pointed to a switch to public transport for trips to the restricted area.
Many cities invest in public transport and active mobility infrastructure alongside zone implementation. These zones also accelerate vehicle fleet renewal. LEZs push older vehicles out in favor of cleaner, compliant models.
However, a study on Madrid found that while it increased alternative fuel vehicle registrations, these were often fossil-fuel powered or PHEVs, not pure ZEVs, suggesting standard LEZs might not fully support deep decarbonization. ZEZs, by design, are explicitly intended to spur ZEV adoption.
Implementation hurdles and socio-economic realities
Despite the benefits, implementation faces significant challenges, particularly concerning public acceptance and socio-economic equity. A primary concern is the financial burden on low-income households and small businesses owning older, non-compliant vehicles, potentially leading to accusations of social inequity.
Mitigation strategies are crucial, including phased timelines, clear communication, and financial support such as subsidies for cleaner vehicles, and exemptions for vulnerable groups.
Investment in affordable public transport is also paramount. Although initial public support is divided, it often grows as benefits become apparent, provided the government adequately addresses public concerns.
Concerns exist regarding costs for businesses, particularly SMEs. However, London’s ULEZ expansion showed no statistically significant negative impact on retail spending in outer London.
Research suggests property values within German LEZs may increase, reflecting the value of cleaner air, though this could raise gentrification concerns. Cost-benefit analyses have yielded mixed results but increasingly suggest health and climate benefits can outweigh costs, especially considering the enormous economic burden of pollution.
Policymakers must communicate the diffuse, long-term costs of inaction versus the more visible, immediate costs of action.
Operational challenges include ensuring robust enforcement, often relying on camera networks and vehicle databases. Managing compliance for foreign vehicles adds complexity. The risk of traffic and pollution displacement outside the zone boundaries is a genuine concern, necessitating a focus on the wider transport network.
The success of these zones hinges on the availability, affordability, and attractiveness of alternative transport options and ZEV charging infrastructure. LEZs and ZEZs are often politically contentious, requiring transparent and inclusive stakeholder engagement with residents, businesses, and community groups to build trust and co-design effective policies.
Stricter zones and innovation
The future trajectory points towards increasingly stringent measures, with existing LEZs tightening standards and many cities setting target dates (often around 2030-2035) for full ZEZ implementation. These zones are the next step for eliminating tailpipe emissions in sensitive urban areas.
Innovation will play a significant role. Cities may explore dynamic pricing based on real-time air quality or congestion. Integrating autonomous vehicles and smart city technologies could enhance monitoring and enforcement and provide better user information.
For urban freight, micro-consolidation hubs and using e-cargo bikes for last-mile delivery are gaining traction. The focus on decarbonizing urban freight, a disproportionate source of pollution, requires strategies beyond simple access restrictions, including financial support and infrastructure development.
Technological advancements in ZEVs and charging infrastructure are critical, but cities must also address data privacy and grid impact and ensure equitable access to these new technologies.
Ultimately, LEZs and ZEZs are integral to a broader transformation towards sustainable, liveable, and climate-neutral urban futures. Their objectives are converging to address air pollution, climate change, and urban liveability goals like reduced noise and improved public spaces. This requires integrated planning across various city departments.
Laboratories for urban transformation
Low—and Zero-Emission Zones have become pivotal instruments in reshaping urban environments. They offer proven benefits in air quality and accelerate ZEV adoption. They also drive positive modal shifts and fleet renewal.
However, they present considerable challenges, especially concerning socio-economic equity, operational complexities like enforcement and displacement, and the significant upfront costs of ZEVs and infrastructure. Navigating political debates and securing public support requires robust stakeholder engagement and communication.
LEZ/ZEZ implementation often transforms cities into laboratories for urban innovation, testing new policies, technologies, and engagement strategies. This global experience provides a rich repository of data and lessons learned. Success requires strategic patience, sustained investment, and a long-term vision, acknowledging that public acceptance and the full benefits often accrue gradually.
Policymakers should embed these zones within comprehensive urban mobility plans. They should adopt phased and adaptive approaches, prioritize equity with targeted support measures,, strategically support ZEVs and charging infrastructure, and collaborate across national and regional levels.
By carefully balancing regulation with enablement, LEZs and ZEZs can be transformative tools for creating cleaner, healthier, more sustainable, and equitable cities.
