Who shouts the loudest? A qualitative study exploring barriers and enablers to implementing a low emission zone in a Northern UK city

Pollution is a major cause of ill health globally. Low emission zones (LEZ) have been identified as effective in reducing pollution and are increasing in popularity but remain divisive. Understanding what factors help or hinder implementation is important. In the UK, Clean Air Zones (CAZ, a type of LEZ) are being implemented in several cities. We aimed to identify key barriers and enablers to the implementation of a CAZ in real time, as policy was being developed and implemented in a large Northern city in England, UK. Twenty-five semi-structured interviews were conducted with city stakeholders and implementors approximately 6 months before a CAZ charging non-compliant taxis, buses, heavy goods vehicles and vans was launched. Thematic analysis was used to analyse data. Implementers were required to operate within a tight policy framework. Key enablers included: freedom to adapt the framework to local context, financial support, and cross-sector working. A focus on health was felt to be useful in justifying the policy to the public. Key barriers included conflict and opposition from local industry, politicians, and communities. Implementation of air quality policy which involves traffic restrictions remains controversial. The voices which 'shout the loudest' are often those with negative views, and these can create divisive discourse which shape public opinion and damage confidence of implementers. A systems perspective is needed to understand socio-political contexts which can influence implementation success. We provide recommendations to other areas considering implementing a LEZ.