Five solutions for urban transport emissions:

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Cars, trucks and buses play a major role in our lives, hauling goods from manufacturers to stores, picking up our trash, delivering packages, and transporting people around cities everyday. But these vehicles also greatly affect public health and climate change. Transport systems can benefit our health, by giving opportunities for physical activity, access to employment, education, health services, food choices and social activities – or increase our health risks through exposure to air pollutants, noise emissions, and road traffic injuries.

The transport sector accounts for almost one quarter of all global greenhouse gas (GHG) emissions and is one of the main contributors to air pollution in urban areas. Transport’s contribution to climate change includes long-lived carbon dioxide (CO₂) and short-lived black carbon generated primarily by diesel vehicles. Studies have linked pollutants from fuel-powered vehicles to all types of adverse effects on organs in the human body.

Addressing vehicle pollution is critical for improving air quality and reducing global warming emissions around the world. Sustainable transport strategies to reduce climate change also have large and immediate health benefits for  the world’s population, especially its most vulnerable groups, such as the poor, older persons, children and adolescents, migrants and refugees, to name a few.

Looking at transport solutions through a health lens can help shape policies that can in turn deliver benefits for health, economic development and climate resilient cities. A number of tools exist to assess, plan and finance healthy and climate-friendly transport.

An important framework for health-promoting transport solutions is “avoid-shift-improve.” Avoid health harming and polluting transport and development policies; shift to healthy, environmentally friendly and active modes of transport; and improve fuel and vehicle technologies.

Here are the top five solutions to address transport emissions:

Solution 1- Encouraging active mobility (shift)

Walking and cycling can bring large improvements to urban air quality and human health. Data from the World Health Organization shows that 9 out of 10 people breath polluted air that exceeds WHO guidelines, leading to 4.2 million premature deaths every year. Additionally, two million people die annually from physical inactivity.

However, policies and infrastructure that improve access for one type of travel, like a highway for cars and motorcycles, may create barriers to pedestrians that would not be able to walk without a bridge. Poorly planned urban transport infrastructure also limits access to parts of the community by displacing residents or consuming public or green spaces.

Some of the attributes of a walkable city include transport decisions that give priority to pedestrians; town planning that is people-centred; housing that is connected to public transport; and regulations and infrastructure that minimise risk to walkers and cyclists from road traffic.

Marginalised groups have less access to private vehicles or public transit, and may be more exposed to certain transport-related health risks. These same groups benefit most from improved public and non-motorized transport, as they bolster independent mobility.

Sustainable transport systems and compact, connected cities, featuring “15-minute self-sufficient neighbourhoods” can promote walking and cycling. Barcelona’s car-free “superblocks” have created safe pedestrian spaces, while several cities including Dublin, London, Addis Ababa and Kigali have made car-free days a regular event on their calendars – encouraging residents to run, walk, cycle and even play sports on the streets. The “walking school bus,” popularized in Japan, has also spread to several cities to encourage independent mobility with safe routes and designated stops for children to walk to and from school.

Solution 2 – Efficient mass transit (shift & improve)

Urban mobility is rapidly becoming one of the greatest challenges facing developed and developing countries alike. According to the WHO, 90 per cent of urban residents are breathing air that does not meet standards for health. Transport is responsible for nearly a quarter of global energy-related CO₂.

Aside from investing in walking and cycling infrastructure, the next best thing city governments can do is invest in greener and more sustainable public transportation. When compared to single occupancy vehicles, public transportation produces 95 per cent less CO₂, 92 per cent fewer volatile organic compounds, 45 per cent less carbon monoxide, and 48 per cent less nitrogen oxide.

Shifting from private motorized transport to public transport, such as rail, metro and bus, is also associated with lower rates of traffic injury risk, reduced traffic congestion, less noise stress and improved equity of access for people without private vehicles.

Aside from reducing the number of private vehicles on the road, mayors in around 100 cities have said that investing in public transport, particularly in electric form, could create 4.6 million jobs by 2030.

Shenzhen in China is the world’s first city to fully electrify its bus fleet. Apart from the noticeable reduction in noise, the city’s 16,000 electric buses emit nearly 50 per cent less C0₂ and much fewer pollutants. Shenzhen Bus Group, the largest of the three bus companies in the city, estimates that an electric bus costs approximately $98,000 annually, compared to $112,000 for a diesel bus.

Solution 3 – Raising emission standards (improve)

Emission standards are legally enforceable regulations that stipulate the allowed rate of emissions into the atmosphere. Raising emissions standards for all vehicles takes heavy polluters off the road and drives market demand for cleaner vehicles.

Cities like London and Oxford have created Low Emission Zones (LEZs) where the most polluting vehicles are prohibited. In some LEZs, the most polluting vehicles have to pay more if they enter the area. Studies conducted in Germany found that hospitals in LEZs diagnosed significantly less air pollution related diseases than those outside of them, making LEZs an effective policy to reduce levels of air pollution in targeted areas.

In Europe, soot-free vehicles are typically vehicles certified to Euro 6. Details of Euro 7, the final standard, will be announced in 2021 and come into force in 2025, before the complete adoption of electric vehicles takes place to further limit climate change and air pollution.

The Climate and Clean Air Coalition (CCAC), Heavy Duty Diesel Vehicles and Engines Initiative, is pushing for major reductions in black carbon emissions through adoption of cleaner fuels and stricter vehicle regulations, particularly in emerging economies where diesel fuel is often of a lower quality. The coalition has worked in Latin America and Asia to produce black carbon inventories, form national task forces and to set target dates for improved national fuel standards.

Solution 3 – Smart land-use policies (avoid)

Integrating transport and land-use policies is another way to reduce emissions by lessening the need for motorised trips. During the COVID-19 lockdowns, several cities enacted policies to allow for “tactical urbanism,” including Oakland, California’s Slow Streets, Nairobi’s Placemaking Week and Mexico City’s #CAMINA with residents working together with authorities to improve access to public spaces and pedestrian safety through signage, reduced road speeds and closed streets to through-traffic.

Travel management strategies reduce overall vehicle use, traffic congestion, road accidents and emissions by mixing mobility choices and land-use policies. These strategies are often implemented by incentivizing alternatives for example, carpool lanes, park & ride stations or subsidized public transport for students, while discouraging personal vehicle use, implementing fuel taxes, parking fees or traffic calming devices.

In addition, by adding thinking about transport in urban spatial planning, policymakers can ensure that residential, business and social activities are located close to mass transit, which will further decrease reliance on cars. Innovative examples include Atlanta’s transit-oriented soccer league, with a network of fields linked to mass transit stations, and Curitiba’s (Brazil) Bus Rapid Transit (BRT) system, where mass transit options are located in dense residential areas.

Solution 5 – Electric vehicles (improve)

In addition to emitting no harmful air pollution, electric vehicles have significantly lower climate change emissions than conventional cars. That is because they produce no direct emissions through the tailpipe and fuelling process. Direct emissions are smog-forming pollutants, such as nitrogen oxides, and GHGs, like carbon dioxide.

Electric vehicles also typically produce fewer life cycle emissions than conventional vehicles because emissions for electricity generation are lower than for burning gasoline or diesel.

The right policies and investments from city and national governments will accelerate the transition to a zero-emissions transportation system. In countries like Norway, as much as 60 per cent of the cars sold in the country in 2020 were electric, while in Kenya where the United Nations Environment Programme (UNEP) has partnered with the Shenzhen Shenling Car Company, rangers are piloting e-motorcycles to move around Nairobi’s 1000-hectare Karura Forest.

(It should be noted that while cleaner vehicle technologies are an important element of air pollution and climate mitigation, reducing reliance on private vehicles and motorized transport is as important, and can yield additional benefits to health. Bus fleet improvements, such as policies mandating the inclusion of particle filters, low-sulphur diesel and the transition from diesel vehicles to compressed natural gas (CNG), electricity, or other alternative fuels, decreases harmful particle emissions.)

Additional resources:

HEAT tool for walking and cycling

WHO Strategies for healthy and sustainable transport

SLOCAT Transport and Climate Change Global Status Report (see: Focus Feature 5: Health Impacts of Transport)

The walkable city