Why are we measuring this?
Nitrogen oxides (NOₓ) are pollutants produced primarily during combustion processes, such as those that occur in older diesel public transport vehicles. NOₓ is a collective term for a group of related gases, the most significant of which for air quality and health purposes is nitrogen dioxide (NO₂). A reduction in NOₓ emissions contributes to better air quality and public health.
A note on this measure: This outcome measure was previously titled and described as tracking "NO₂ emissions." The emissions model we use calculates total NOₓ output from the fleet, not NO₂ specifically, and we do not currently apply a validated NO₂-only conversion. We have corrected the title, target and description of this measure to accurately reflect that it reports NOₓ. The underlying data and reported tonnage figures are unchanged — only the labelling has been corrected.
This is aligned with the Government Policy Statement on Land Transport and the Ministry of Transport Te Manatū Waka’s Outcomes Framework, as well as included in the Regional Public Transport Plan and the Regional Land Transport Plan.
By analysing this data, we can understand the trends in emissions from public transport, assess the effectiveness of policies and initiatives aimed at reducing fleet emissions, and identify areas needing further improvement.
How do we measure the result?
We track kilometres travelled by each engine type and then use an emission model to calculate NOₓ emissions produced by our public transport services. This model estimates total nitrogen oxides output; it does not currently separate out the NO₂ fraction specifically.
What work have we undertaken to contribute to this outcome?
The reduction in NOₓ emissions in 2025/26 indicates a clear improvement in fleet emissions efficiency. The primary contributing factor is the continued transition toward a cleaner fleet composition.
A new electric double-decker bus was added to the fleet in February 2026 for a 12-month trial. This is the country’s first lightweight electric double-decker making it the first vehicle of its kind in the country to operate without a special permit. The bus has been trialed on the Route 7 Halswell-Queenspark service and will be tested on several of Metro’s busier routes over the trial period, allowing us to assess its benefits and consider our options going forward.
In April 2026, Timaru’s on-demand public transport service, MyWay by Metro, became fully electric with the introduction of 10 new electric vehicles (EVs), eliminating tailpipe emissions from this fleet and delivering quieter, cleaner journeys for the Timaru community. Six of the new vehicles are “Very Small Buses” (VSBs), a first for New Zealand, with the remaining vehicles similar to those already in service.
At the end of 2025/26, 26 per cent of our urban Greater Christchurch fleet and Timaru was electric.
We have also moved electric buses onto routes where they can travel the most kilometres. Together with the new vehicles described above, this means 31 per cent of fleet kilometres are now travelled by zero-emission buses, up from 29 per cent last year.
Through the Annual Plan 2025/26 process, we have had to delay funding for EV replacement and infrastructure as part of meeting government expectations around private revenue. This means we will not have funding available over the coming year to add additional EVs to the fleet.
Who else plays a role?
We can implement policies, provide funding, and enhance the sustainability of the public transport fleet to reduce emissions. This includes modernising our fleet, optimising routes, and implementing policies that promote public transport usage over private vehicles.
Partner councils, such as Christchurch City Council, Waimakariri District Council and Selwyn District Council, play a significant role by providing and maintaining the infrastructure required for public transport to reduce reliance on private vehicles.
National transport agencies, the Ministry of Transport Te Manatū Waka and NZ Transport Agency Waka Kotahi have the ultimate influence over public transport due to their key roles in setting national transport policies and funding for public transport.
Where can I find more information?
Find out more about transport emissions.
Learn about our transition to low-emissions actions in our Climate Action Plan.
Download the 2024/25 results for N2: Tonnes of NOₓ emissions from the public transport fleet is decreasing (PDF file, 801.3KB)
