New research on Glasgow’s Low Emission Zone (LEZ) reveals that, while traffic flow has remained largely unchanged since its implementation, air quality has notably improved.
Co-authored by researchers from the Universities of Auckland, University College Dublin, and Glasgow, the study gathered hourly data from traffic sensors and air quality monitors in the city’s busy Hope Street and High Street within the LEZ to produce figures for the daily average NO2 (Nitrogen Dioxide). Meteorological data, provided by the UK Met Office, factored in the wind effect on NO2 dispersal.
The study found a statistically significant reduction in traffic flow on High Street during weekdays resulting in notable decreases in normalised NO2 levels of between 25%-27% on weekdays. A 35% drop of NO2 on weekends was also observed.
In contrast, traffic patterns on Hope Street remained stable, yet statistically significant decreases in NO2 levels of between 9-13% on weekdays were still observed, suggesting the establishment of the LEZ discourages high emission vehicles in the city centre and helps improve air quality.
Co-author of the paper, Qunshan Zhao, Professor in Urban Analytics at the University of Glasgow’s Urban Big Data Centre, said:
“These early results indicate that while traffic reductions and the decrease of the high emission vehicles in some parts of the city may be contributing to improved air quality, other factors may also play a role. The findings highlight the need for continued monitoring to better understand the LEZ’s long-term impact on both traffic and pollution levels across Glasgow. Paired traffic sensors and air quality sensors can be set up to help further understand the relationships between traffic flows and air quality variations.”
In common with other large UK cities, Glasgow has high traffic volumes from both private vehicles and Heavy Goods Vehicles (HGVs). In 2021 alone, the city had nearly 240,000 licensed vehicles, according to the Department for Transport Statistics. The resulting congestion led to elevated emissions of nitrogen oxides (NOx) and particulates from vehicle-related activities such as tailpipe emissions, brake wear, tyre wear, and road abrasion.
Responding to growing concerns about traffic-related air pollution, Glasgow City Council introduced a Low Emission Zone (LEZ) in the city centre on 1 June 2023 with the aim of reducing pollution by restricting access to vehicles that do not meet strict emissions standards.
There are currently Clean Air Zones and Low Emission Zones in the following UK cities: London, Birmingham, Bristol, Oxford, Bath, Bradford, Portsmouth, Newcastle, Sheffield, Southampton, Aberdeen, Dundee, Edinburgh and Glasgow.