General

• We spend 6% of our time commuting, but that time accounts for 30% of our exposure to some air pollutants (Gary Fuller et al., 2023)
• UN Decade of Sustainable Transport taking place from 2026-2035
  
  • Especially important now because “globally, transport accounts for about 20% of total greenhouse gas emissions, and transport emissions are predicted to increase a further 60% by 2050 in a business-as-usual scenario” (Johnson & Holzman, 2025)
• US EPA reported that combined emissions from industry, electric power, and transportation contribute 76% of carbon air pollution (McKelvey, 2025)

Cycling

• Injuries caused by electric bikes, e-scooters (e-cyclist) double each year (Paul Day, 2024)
• Cyclists wear helmet 53% of time, e-cyclists wear helmet 44% of time (Paul Day, 2024)
• Cyclists driving over legal alcohol limit is 4%, while e-cyclist is 7% and e-scooter is 9% (Paul Day, 2024)
  
  • Less safety measures, more risk-taking behaviour on electric vehicles
• Educational campaigns needed to promote helmet use and sober riding (Paul Day, 2024)
• 4% of commuters in England use bicycles (Gary Fuller et al., 2023)
• Cities currently build only one-tenth of the cycling infrastructure they need to meet global climate targets (Guo et al., 2025)
• 2% of trips shorter than 3 km were made by bicycle in the UK, and over 50% of trips range between 2–3 km – yet these journeys are frequently made by car (WHO, 2025)
• Cycling benefits include: reduced carbon emissions, reduced air/noise/water/soil pollution, reduced ecosystem loss, better quality of life, lower diabetes risk, healthy weight, better cardiovascular health, reduced risk of cancer, space efficiency, road congestion relief, convenience for short trips, reliance and accessibility, reduced infrastructure costs (WHO, 2025)

Public Transport

• Tube dust made of metal particles, organic matter, mineral dust.  Often comes from track and wheel wear and breaking (Mayor of London)
• Modern braking systems are being introduced in 2025 to create less dust in the tube (Mayor of London)
• Due to poor ventilation, dust can be resuspended as trains arrive, so platforms have worse air quality in comparison to ticket halls and operator cabins (Sarah Collins, 2022)
• PM2.5 is much higher on the Underground than any other transport mode (2022)
• Dust exposure can be reduced by the platform screen doors (seen in newer section of Jubilee and Elizabeth Line) as well as improving ventilation (Filipa Adzic, 2023)
• Largest factor for in-train particle concentrations was presence of tunnels for black carbon (factor of 40), PM (factor of 6), PNC (factor of 7) (Anna Font et al., 2024)
• Engine fuel largest impact on NO2 by factor of 14 (diesel vs electric times for hybrid trains) (Anna Font et al., 2024)

Walking

• Walking is least exposed mode for several pollutants (Marie Ramel-Delobel et al., 2024)
• Active modes (cycling and walking) have little contribution to air pollution emissions as well as health benefits.  But, physical exercise means faster breathing, so may increase inhaled air pollution by 50% when compared to drivers (Marie Ramel-Delobel et al., 2024)
• 10% of commuters in England walk to work - 32% of all transportation journeys (Gary Fuller et al., 2023)
• In many African cities, 78% of people are walking for travel every day with inadequate infrastructure (WHO, 2025)

Vehicles

• Self-pollution of passive transport and neighbouring vehicles cause emissions to enter ventilation system (Marie Ramel-Delobel et al., 2024)
• Car users have highest in-vehicle air pollution - 70% higher exposure than cyclists for certain pollutants (Gary Fuller et al., 2023)
• Highest to lowest pollution sources: cars and vans, bus, cyclist, walking, but exposure depends on surrounding traffic as well as other sources.  For example, pedestrians are exposed to 1.5-7 times more pollution on high-traffic routes (Gary Fuller et al., 2023)
• In Delhi, India, up to 45% of air pollution was estimated to be caused by transport, with private cars and motorcycles accounting for most transport emissions (WHO, 2025)
• Automobiles cause 1 in 34 deaths (Miner et al., 2024)
  
  • Crashes alone cause 1.3 million deaths, including 700 children each day
  • Pollution from automobiles cause 370,000 deaths per year
  • “Beyond impact injuries, more than 90% of people live in areas with unsafe levels of outdoor air pollution including vehicle-sourced pollution (World Health Organization, 2021b)”
• Up to 90% of urban PM is traffic-related (Reis et al., 2018, p. 252)
• Diesel engines release 10-100x as much breathable PM as gasoline engines (Mazzarella et al., 2007)
• Air pollution from automobiles caused by motor running and material abrasion (Miner et al., 2024)
  
  • Abrasion emissions may increase with transition to electric cars, as they are often heavier
  • Manufacturing and disposal also contribute
  • Road dust contains high levels of dangerous metals like lead
    
    • Before leaded fuel was banned, it “accounted for 80-90% of airborne Pb in cities where it was used” (van der Kuijp et al., 2013, p. 1)
• More people who use active travel means less emissions for them to be exposed to from vehicles (Marie Ramel-Delobel et al., 2024)

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