Introduction In cities across Southeast Asia, people and goods move through roads by way of cars, trucks, motorcycles, bicycles, and public transport vehicles. However, the often-invisible cost of these journeys is the impact of transport-related air pollution (TRAP), which accounts for up to 80% of all air pollution in Southeast Asian cities. A successful innovation to address TRAP globally has been low-emission zones (LEZs)—areas that restrict the entry of the most polluting vehicles or impose entry fees on them, creating a clear incentive for cleaner transport choices and helping to accelerate the transition to low and zero emission fleets. While LEZs have been proven effective in several cities globally, the transport context in Southeast Asia requires a considered approach to address barriers that would allow such a policy tool to have the desired impact. TRAP Impacts TRAP in Southeast Asian cities adversely affects public health. It can heighten respiratory and cardiovascular conditions, making air pollution one of the leading risk factors across the region. In addition, air pollution discourages people from active modes of travel that promote physical health, such as biking and walking. Air pollution also significantly impacts the economy. It increases strain on healthcare services, congests roads resulting in significant delays, and leads to productivity losses as people suffer from air pollution-related diseases and fail to report for work. Thus, approaches to reducing TRAP are vital in support of a range of Sustainable Development Goals (SDG), including Good Health and Well-being (SDG 3), Sustainable Cities and Communities (SDG 11); and Climate Action (SDG 13). Considerations for LEZ Implementation Can LEZs improve air quality in Southeast Asia? The answer might not be as straightforward as it sounds. First, cities need to understand if the underlying source of local air pollution is indeed transport. Many cities do not have sufficient air quality monitoring or emissions inventories to make this determination. Second, the successful adoption of LEZs requires a foundational ecosystem of polices and infrastructure that many countries and cities in the region lack, including comprehensive public transit, stringent and unified emission standards, digital registration and enforcement, freight management, and programs that enable fleet modernization and the transition to lower-emission vehicles. How can Southeast Asia start taking concrete measures to reduce TRAP and/or design a future LEZ? To answer this question, it is useful to consider a range of different topics. Transport modality and infrastructure gap LEZs and other TRAP reduction schemes primarily focus on removing or restricting the access of polluting vehicles. This often leaves key questions for daily commuters as to how they will travel to work or school and how they will be compensated for a vehicle they cannot use. Shop owners and freight forwarders may also be concerned with how they will meet delivery schedules or attract customers who may be used to traveling to their stores by private motor vehicle. A safe, reliable, and affordable public transport and an active transit system are critical to any proposed LEZ scheme, alongside transitional support to help residents and businesses adapt to new requirements. In the absence of such a setup, the scheme will have an unfair impact on persons who have no reliable alternatives to using their polluting vehicles. As an example, large, geographically spread cities such as Jakarta and Manila have significant issues relating to multi-modal integration, which would make immediate LEZ adoption a great challenge for many people. Therefore, it is important for cities to take into account the critical system requirements for successful LEZ adoption: affordable and accessible low or no-emission public transit systems; networks of active mobility infrastructure, including pedestrian and cycling pathways; affordability initiatives, including compensation and exemption schemes in select low-income zones, and incentives for public transit use; electric charging networks for cars, public transport, and freight vehicles; urban freight consolidation hubs and electrified "last mile" freight delivery mechanisms to ensure deliveries can still reach all areas; and last mile connectivity for the public and freight. Enforcement, engagement, and governance Apart from transport infrastructure, coordination on the design or implementation of vehicle restrictions need to also be considered. The fragmentation of stakeholders responsible for TRAP reductions is a core issue, given that environmental agencies often set air quality targets, but transport and municipal agencies manage roads and transport. Successful adoption of an LEZ requires an integrated policy, enforcement, and community engagement framework shared among all key stakeholders. Cities should ensure a strong system of registration and enforcement, with the need to include emissions testing linked to centralized digital vehicle registration systems; CCTV and/or number plate recognition cameras linked to a centralized database; incentives for people to use public transit systems, such as affordability measures or subsidized travel; accessible web platforms for vehicle registration and requisite digital literacy training for the public; and regulatory powers to enforce restricted access for polluting vehicles and the authority for agencies to issue fines for non-compliance. Community engagement is also vital as residents and businesses need to adapt to significant changes in their current systems. They must be made aware of the health and economic benefits of adoption and should easily be able to comply with new regulations in relation to registration and enforcement. This highlights the importance of a phased approach that ensures communities have the opportunity to understand the rationale for change and accordingly adjust their behavior. Implications Southeast Asian cities can explore low-emission zones (LEZs) to support the transition to cleaner air for all and support progress toward SDGs 3, 11 and 13, which all relate to less transport-related air pollution (TRAP). However, it is essential to understand the realities of both the enabling environment for their adoption and for the systems required for its effective and community-accepted implementation. Comprehensive preparation, understanding of barriers, and specific analysis of Southeast Asian cities and governance frameworks are pivotal in the successful adoption of LEZs and TRAP reduction schemes. An upcoming LEZ Maturity Assessment Framework being produced by the Asian Development Bank will directly support this process and enable governments to step forward with confidence in the implementation of these vital approaches to addressing TRAP and its associated impact on health and well-being across Southeast Asia. Resources Asian Development Bank. Advancing Low Emission Zones in Southeast Asia. C40 Cities Climate Leadership Group. 2023. How to Design and Deliver a Low Emission Zone. Implementation Guide. F. Moore et al. Low Emission Zones and Urban Logistics: How Can We Make It Work? Urban Logistics as an On-Demand Service. M. Taylor. 2025. Dramatic Fall in London’s Levels of Deadly Pollutants After Ulez Expansion. The Guardian. News Article. 7 March. N. McCarthy. 2020. This is the Global Economic Cost of Air Pollution. World Economic Forum. News Article. 18 February. Ask the Experts Rebecca Stapleton Principal Transport Specialist, Sectors Department 1, Asian Development Bank Rebecca Stapleton leads sustainable and inclusive transport initiatives across Asia and the Pacific at ADB. Her work focuses on low-emission transport, urban mobility, road safety, air quality, and electric mobility, integrating policy, investment, and institutional reform to deliver practical development outcomes. Follow Rebecca Stapleton on Honor Puciato Associate Director, Ricardo Energy & Environment, WSP Group Honor Puciato has more than 17 years of experience leading the delivery of complex emissions mitigation strategies, with a focus on hard-to-abate industries such as transportation. Her work on policy, regulation, and the implementation of decarbonization and air quality improvement programs spans Asia, EU and the UK. Follow Honor Puciato on Blaise Murphet Global Consultant, Crossroads Consulting Blaise coordinates mobility and transportation programs. He has worked with governments, and multilateral and non-governmental organizations in more than 40 countries. He works with transport leaders through Crossroads Consulting to support initiatives in safe and sustainable mobility. He serves as an Honorary Fellow at the George Institute for Global Health. Follow Blaise Murphet on Leave your question or comment in the section below: View the discussion thread.