CAZs (or Low Emission Zones, LEZs) have been shown to deliver significant improvements in air quality – for example, London’s ULEZ has achieved a 27% reduction of NO2 levels across the entire capital since 2019[1], whilst Paris’ CAZ has contributed to a fall in PM2.5 concentrations of 55% since 2005[2].
While these policies can deliver real improvements, their success depends not just on technical design, but on how well they reflect the unique characteristics of the city. London’s Ultra Low Emission Zone (ULEZ) has become one of the most closely studied examples of urban air quality policy. Since 2019, it has delivered substantial reductions in NO2, supported by strong public transport, targeted scrappage schemes for older vehicles, and sustained public engagement. Paris has taken a similarly ambitious but distinctly local route. Through its “Zone à Faibles Émissions” (ZFE), Paris has gradually restricted high-emission vehicles while promoting walking, cycling, and electric mobility. Crucially, the city has linked clean air measures to broader urban renewal—expanding bike lanes, greening streets, and rethinking public space. In both cities, restrictions were matched with viable alternatives and visible public benefits, creating policies that feel purposeful rather than punitive.
Asia’s urban environments are extraordinarily diverse, from the vast sprawl of Delhi and Jakarta to the high-density, transit-oriented cities of Seoul and Singapore. Their pollution sources, transport systems, and social structures differ dramatically, and in most cities, vehicle emissions are just one element of a complex mix that includes industrial pollution, construction dust, and seasonal crop burning. A CAZ in such a setting must therefore be part of an integrated air quality strategy, rather than a stand-alone transport policy.
Some Asian cities have already established CAZs. Seoul’s Green Transport Zone, launched in 2019, targets older diesel vehicles while expanding electric mobility and improving public transit. Singapore, with its long-standing vehicle quota and electronic road pricing systems, provides another model of managing emissions through strong governance and demand management. These examples demonstrate that when clean air policies are tailored to local contexts—and supported by investment, communication, and equity measures—they can be both effective and publicly acceptable. Many other cities are in the process of developing similar policies – for example, in Kazakhstan’s largest city, Almaty, work is underway to implement the country’s first LEZ, involving paid entry for older vehicles and incentives for cleaner vehicles starting around 2027.
The experiences of cities such as London, Singapore and Paris show that success of CAZs should not be measured by air quality data alone. Cleaner air must be achieved alongside accessibility, economic resilience, and social inclusion. The most effective low emission or clean air zones are those that are co-created with the public—built on consultation, transparency, and shared benefit.
Logika Group's Dr Clare Beattie will be speaking at the UNEP Clean Air Week in Bangkok on November 24th 2025 on successful approaches to the design and implementation of impactful and inclusive clean air zones. Tom Buckland will also be attending and welcomes the opportunity to connect and explore opportunities for collaboration in international air quality and climate projects.
If you’re interested to hear more about Logika Group's work in this area, please get in touch here.
[1] New evidence reveals that all Londoners are now breathing cleaner air following the first year of the expanded Ultra Low Emission Zone (ULEZ) | London City Hall
[2] Air pollution in Paris region 'cut in half' over the past 20 years
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