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COVID-19 Lockdowns Show Positive Impacts on Traffic Flow and Air Quality in Oxford

Researchers looked at how the COVID-19 lockdown measures impacted the traffic flow and the concentrations of pollutants in Oxford’s atmosphere.

Air pollution is responsible for an estimated 28,000-36,000 early deaths in the UK every year. It is one of the top 5 causes of deaths in urban environments, causing more deaths than road traffic accidents and harsh winter conditions. 

Some measures are already being rolled out to try to reduce pollution, such as car manufacturers producing lower emission vehicles and cities instigating measures such as Low, Ultra Low or Zero emission zones including a zero emission zone in Oxford. However, it is important to judge how effective these strategies are to know how much pollution is reduced by limiting traffic in certain areas. Researchers need data to compare the same regions with high and low average levels of traffic and over long periods to account for changes in weather and times of day for example. 

On 23 March 2020, the UK went into its first lockdown to slow down the spread of COVID-19. With non-essential workers staying at home, so did their vehicles with car usage reduced by 77.% in the first lockdown. This lockdown, and subsequent lockdowns, provided a unique time for researchers to analyse the effects of reduced transport and emission of pollutants into the atmosphere.

A recent study, co-authored by Professor Felix Leach from the University of Oxford’s Department of Engineering Science, has found that emergency public health measures introduced during the COVID-19 pandemic have had a positive impact on traffic flow and air quality in cities in the United Kingdom. The study analysed real-time air quality and traffic data from Oxford, UK, and found that the first national lockdown resulted in a 77.5% reduction in cars on the road and substantial reductions in daily mean concentrations of oxides of nitrogen (NO and NO2). In contrast, daily mean NO and NO2 concentrations increased during the second lockdown despite the reductions in traffic.

The study also found that the second lockdown saw a relative increase in the contribution of buses and goods vehicles to NO2 and NO levels at the roadside, compared to the first lockdown. The results also showed that reduced demand for transport could mitigate peak magnitude concentrations of transport-related pollutants but could also be associated with increased ozone levels.

The authors of the study emphasised the importance of further research to evaluate the effectiveness of national and local interventions to deliver environmental and health benefits in small UK cities, and to inform effective public policy decisions. They also emphasised the importance of sharing best practices to address the challenges of reducing carbon emissions from the transport sector in similar settings worldwide.

The findings of this study provide valuable insights into the positive impacts of COVID-19 restrictions on traffic flow and air quality and highlight the importance of reducing personal transport demand to improve air quality and protect public health. As cities worldwide continue to recover from the pandemic, this research serves as a reminder of the potential benefits of reducing personal travel and embracing alternative modes of transportation.