Shaping smarter transportation habits and reducing pollution

Vehicle emissions are a primary cause of air pollution, posing a threat to respiratory, cardiovascular and reproductive health, as well as a variety of cancerous and non-cancerous ailments. In all of its forms, air pollution is responsible for more than 6.5 million deaths each year worldwide.  Vehicle emissions also trap atmospheric heat contributing to rising global temperatures, can contaminate waterways, and have other adverse environmental impacts.   

In 2022, Britain’s first Zero Emission Zone (ZEZ)  scheme based on road user charging was launched in Oxford. Created in partnership by Oxfordshire County Council and Oxford City Council,  and supported by Trellint, the scheme aims to reduce harmful CO2 emissions and air pollutants and to shape smarter transportation habits. The scheme uses advanced imaging and data analytics developed and operated by Trellint drawing on information from multiple databases and with minimal on-street infrastructure.


In their ZEZ plan, the two councils identified nitrogen dioxide (NO2) as the air pollutant of most health concern in Oxford as there can be no safe volume of it in the atmosphere.

The Councils sought to improve air quality and reduce NO2 and CO2 emissions without an abrupt disruption of life in the community, while also educating citizens about how their choice of transportation impacts emissions levels in the community.

The UK’s Environmental Improvement Plan (EIP), which was updated in 2023, outlines actions to help revitalise and restore the environment through pollution reduction measures. It reaffirms a commitment to reduce PM2.5 emissions (i.e. particulate matter with diameters of up to 2.5 micrometres), which are inhalable and of concern to both public- and environmental-health.

The ZEZ project aligns with both short- and long-term goals of Oxfordshire County Council and Oxford City Council and with the EIP.


Trellint partnered with Oxfordshire County Council to identify, develop and implement systems to support the ZEZ pilot’s operation and enforcement.

Trellint’s experts designed a system to identify and log vehicles being used in the Zero Emission Zone via vehicle registration mark (VRM) data captured by Automatic Number Plate Recognition (ANPR) cameras. The system uses the VRM to check the vehicle’s emissions output via multiple data sources against an established rule scheme to determine the charge, if any, that is payable.

The scheme uses emissions data as a key driving factor focusing on each vehicle’s engine emissions standards and on the number of grammes per kilometre (g/km) of CO2 produced by each vehicle, rather than solely relying on vehicle class or engine type. Rather than doing a simple look-up for the details of one vehicle, Trellint’s system interfaces with multiple vehicle data sources, making decisions in real-time which sources are required for each vehicle lookup. The solution evaluates the response from the initial Driver and Vehicle Licensing Agency (DVLA) query, and only requests data from additional sources if required information is missing, or if there are inconsistencies in the records.

The ZEZ software not only looks for missing data but uses proven logic to detect disparities in the information known about the vehicle. This logic enables the system to determine whether the emissions data is correct and, therefore, whether further lookups are required. This ensures that ZEZ has a complete and accurate picture of the vehicle, rather than just relying on one data source.

In addition to these checks the system also performs lookups to lists of exempt and discounted vehicles before determining the daily ZEZ charge for the vehicle and is integrated with the public facing payment portal.

The ZEZ pilot charges polluting vehicles used on certain streets between 7 a.m. and 7 p.m. daily. Zero-emission vehicles, such as electric cars, can be used in the zone free of charge. All petrol and diesel vehicles, including hybrids, incur a daily ZEZ charge of up to £10 unless they have a discount or exemption.

 “The scheme is attracting substantial interest among other authorities both within and beyond the UK. Its successful implementation sets a precedent for authorities looking to implement emissions-based charging schemes.”

Bryan Evans, Senior Transport Planner, Oxfordshire County Council


  • In 2022, monitoring by Oxford City Council reported a citywide NO2 decrease of 8% compared with the previous monitoring year.
  • Of the 90 monitoring sites across Oxford where air quality was available for comparison, the majority (80) reported decreases in NO2 levels, with only 10 reporting increases.
  • According to data provided by Oxfordshire County Council, traffic levels increased (on average) by 8.2% in Oxford in 2022. NO2 levels reduced in the city despite these traffic increases.
  • Compared to the levels of NO2 measured in 2019, the last pre-pandemic year, the average NO2 levels were 24% lower in the city in 2022.

In addition, data collected in 2022 reveals that NO2 reduced by 12%, 14% and 18% on New Inn Hall Street, Cornmarket Street and St Michael’s Street respectively in the ZEZ pilot area.