Air quality improves as EV bus numbers increase

A new report from Greater Wellington’s Environmental Science team shows the positive impact Metlink’s EV buses are having on Wellington’s air quality along the Golden Mile, leading both to positive health benefits and climate change mitigation. 

The Metlink bus fleet emissions 2021/22 Environmental impacts annual report outlines air monitoring and bus emissions tracking tool results up to 30 June 2022 and reports on monthly emissions and annual air quality performance indicators.  

“The report shows that greenhouse gases and air pollution from Metlink’s public bus network have trended down since September 2021 as the proportion of kilometres travelled by electric buses increased relative to diesel services,” says Senior Environmental Scientist Tamsin Mitchell.  

An increase in the proportion of electric buses travelling on Manners Street, for example, was associated with reductions in pollutants. Diesel particulate air pollution reduced by 28% and nitrogen dioxide (NO2) by 18%. 

“Lower total emissions from the Metlink bus fleet are very welcome, and the health benefits of Greater Wellington’s investment in EV buses are clear from a corresponding decrease in harmful emissions, including particulate matter.” 

Nitrogen dioxide causes respiratory and cardiovascular system damage – making people more prone to infections and diseases such as asthma.  

The latest Health and Air Pollution in New Zealand study, 2016, found that such problems worsened by air pollution contributed to more than 3300 premature deaths nationwide, and cost $16 billion in a single year. Two thirds of those deaths could be attributed to vehicle emissions.  

Figures for the Wellington region are equally sobering. Nitrogen dioxide (N02) contributed to 162 early deaths, 667 hospitalisations for respiratory and heart conditions, as well as 1,183 childhood asthma cases. 

According to Metlink General Manager Samantha Gain, Greater Wellington also sees a reduction in air pollution as a regional climate change mitigation priority. 

“Metlink’s bus fleet currently makes up around 35% of Greater Wellington’s corporate carbon footprint, so electrification of the bus fleet will contribute to meeting Greater Wellington’s target of becoming carbon neutral by 2030.  

“Our target is for all core service bus routes to be electric-only by 2030 and we’re working towards complete decarbonisation of the bus fleet by 2035. We currently have 90 EV buses – or 20 per cent of our fleet - and plan to have 108 by 2023, which will further boost proportion of the EV buses in the fleet to 22 per cent, which is high by international standards. 

“But bigger gains in reducing carbon across the region will, however, be made by encouraging mode shift away from cars to active and public transport.” says Samantha Gain. 

“This involves regional initiatives such as Let’s Get Wellington Moving, intensification of urban development and the Wellington Rail Programme Business Case, a 30-year customer-driven strategic investment plan.

“The business case outlines what’s needed beyond current investment to help drive the region’s economic development and social wellbeing in an environmentally and socially sustainable and resilient manner.

“It covers the passenger services and infrastructure needed to deliver a modern transit system, and the network infrastructure required to support this system while also enabling a growing freight operation. 

“The outcome of these initiatives will be two-fold – improving air quality and progress towards a sustainable, low carbon regional economy”.