York study finds post-lockdown UK traffic getting back to normal but air remains cleaner as congestion is down
Air pollution is lower than expected in some of the UK’s towns and cities, despite a return to almost normal traffic levels, according to a new study by researchers at the University of York. The study’s findings show that while road traffic is getting back to pre-lockdown levels, some concentrations of air pollutants such as nitrogen dioxide (NO2) are still lower than expected.
The researchers suggest that factors such as staggered commutes and homeworking is reducing congestion, which plays a factor in air pollution.
Dr David Carslaw from the Department of Chemistry has been analyzing data from roadside monitoring sites across the UK throughout the lockdown. This has included monitoring concentrations of NO2, which is a key pollutant caused by vehicles.
On average across the UK, NO2 levels were 56% lower than normal at the height of lockdown and as of 1 July, with many restrictions currently lifted, they remained about 30% lower. In York NO2 levels were 52% lower than normal at the height of lockdown and as of 1 July, with many restrictions currently lifted, they remained about 18% lower.
The data across the UK showed a deep plunge after lockdown for concentrations of nitrogen dioxide of around 50% on average nationally and a slower recovery. Things are not back to normal according to the air quality data. It seems that while traffic levels look like they have mostly returned to normal, concentrations of some air pollutants are still quite a lot lower than expected. We think the reason is that congestion has not fully returned, and this has quite a large effect on emissions and hence concentrations.
Trying to measure the impact on air pollution of congestion is very challenging as there are so many factors that affect emissions. The analysis of data gathered during lockdown and coming out of lockdown might give researchers an opportunity to better understand more about linkages between air pollution and congestion.—Dr Carslaw
Dr Carslaw’s team has been analyzing data from more than 100 sites across a wide range of towns and cities in the UK as part of ongoing research into concentrations of roadside air pollutants.