Electric buses in Oxford: Reducing air and noise pollution
This case study highlights the Zero Emission Bus Regional Area (ZEBRA) scheme, a phased implementation of 159 battery electric buses in Oxford from 2022-2024, undertaken by the University of Birmingham, University of Oxford and Oxford County Council.
Transport is a major source of both air and noise pollution, particularly in urban areas. Exposure to long-term noise pollution can damage hearing, negatively affect mental health, disturb sleep, and contribute to chronic conditions including cardiovascular disease.
Replacing older diesel vehicles with electric vehicles offers an opportunity to significantly reduce harmful emissions and reduce noise pollution. However, there is still limited evidence on how the transition to electric buses affects the health of people living and travelling in UK cities.
In Oxford, noise pollution is recognised as an public health issue. As a compact city with a large transient population of students, residents and commuters, Oxford experiences high levels of traffic congestion. This contributes to poor air quality and high levels of road traffic noise across the city.
In 2022, funding was secured for the Zero Emission Bus Regional Area (ZEBRA) scheme. This scheme saw a phased replacement of 159 diesel buses with electric buses by November 2024. These buses are now used along 34 routes serving Oxford and surrounding communities. The scheme’s aim was to improve air quality, reduce noise pollution, and support efforts to reduce traffic levels and congestion in the city.
Evaluation
The University of Birmingham, University of Oxford, Oxford County Council and Oxfordshire County Council worked in partnership to understand the impact of the rollout, including changes in noise levels, experiences of bus users, and the potential benefits for public health.
An NIHR funded evaluation was undertaken to assess the benefits of the scheme. Baseline monitoring of noise around Oxford City was performed through 16 low cost audio sensors (Audiomoths) at static locations in 2024 prior to the ZEBRA bus roll out. This was repeated in 2025 after the intervention. These static deployments were used to determine a ‘Traffic Noise Index’ around the city, i.e. noise pollution from vehicular traffic only, including on otherwise pedestrian and residential streets. In addition, four audio sensors were installed on buses (two diesel and two electric) to directly compare in-vehicle noise levels and assess the influence this may have on the driver and passengers.
The analysis was co-designed with Oxford-based stakeholders and combined quantitative and qualitative methods (outlined in Table 1 below) to determine the effectiveness of the ZEBRA scheme and its feasibility and acceptance to help inform future rollouts of the scheme elsewhere.
Research AIm | Quantitative methods | Qualitative methods |
|---|---|---|
Effectiveness | Air quality monitors, Noise sensors | Key stakeholder interviews, Resident and commuter focus groups, Intercept interviews |
Feasibility and Acceptability | Health and economic assessment | Key stakeholder interviews, Resident and commuter focus groups |
Evaluation design | Logic model development and Methodological advances | |
Table 1: Research methods
Further information is available at https://phirst.nihr.ac.uk/evaluations/zebra-scheme-oxford/
Some delays were experienced in the rollout of the ZEBRA fleet, with electric buses introduced over a longer period than originally planned.
There were also delays to parts of the research process, including stakeholder interviews assessing the implementation process and efficiency of the roll out. However these delays did not adversely impact the study.
The rollout of electric buses in Oxford has had a measurable impact on reducing traffic-related noise pollution across the city. Static monitoring showed reductions in Traffic Noise Index levels ranging from 0.3 to 6 dB, with an average reduction of 5.1 dB. Peak noise levels also reduced substantially in areas served by electric buses, while most control locations experienced increases in noise pollution (from 1 to 10 dB at three of the four locations).
On-bus monitoring found that battery electric buses were significantly quieter than diesel buses, with noise levels typically 20–30 dB lower. Further analysis into the diurnal noise from the two bus types showed diesel buses were consistently around 15 dB louder during operation, the equivalent of thirty-two times the acoustic dose.
The transition to electric buses also improved people’s experience of travelling through and spending time in the city. Residents and passengers reported reduced exhaust smoke and diesel fumes, contributing to a cleaner and more pleasant streetscape. Bus users also described improved ride quality, accessibility, and a sense of civic pride - feeling that their city cares for them. However this had limited impact on their bus use due to wider impacts such as cost, reliability and route connectivity.
Oxford’s compact layout and dense bus network made it well suited to rapid implementation of the ZEBRA scheme. A key factor in success was strong collaboration between bus operators and local authorities, underpinned by a shared vision for improved public transport services.
For other areas considering similar schemes, collective planning, co-operation and partnership between local transport authorities, bus operators and suppliers is essential to manage practical and logistical implementation challenges.
Public communications also play a vital role in the public impact of bus electrification schemes. Customising bus fleets with a consistent brand identity can raise awareness of scheme benefits.
While bus electrification can contribute to improved air quality, better public health outcomes, and progress towards net zero transport, wider structural issues such as congestion and service connectivity still need to be addressed to fully realise increases in bus use.
Noise Action Week Case Study Bank
Noise Action Week celebrates organisations that are making a real difference in managing noise and improving health and wellbeing for their communities. We have developed a 'living' bank of case studies showcasing local authorities, businesses, and other organisations that demonstrate good practice in noise management.
If you have a suggestion for a case study, please contact the Noise Action Week Coordinator Ellie Savage (ellie@the-ies.org).
Image credit: Suzanne Bartington
