September 6, 2022

Installing “Tredges” Around Schools Significantly Lowers Air Pollution for Students

We still have this idea that we can drive our way out of congestion, not factor in the cost of more vehicles on the road even if they are electric, and still think that driving kids to school should be a right, instead of a drawback. Much of how we plan cities is not based on the most precious assets of society, children, where they learn, where they play, and where they live.

We need to reimagine schools as central places, and design and mitigate hazards to allow students to thrive.

Viewpoint Vancouver has already written about the importance of mitigating noise around schools, and advocated for school traffic calmed areas around schools, not just single streets. 

This study published in PLOS Medicine  found that children exposed to triple the amount of vehicular traffic on roadways were 23 percent slower in cognitive development and had less attention spans, five percent slower in a year. This study shows that noise can also impact cognitive development by producing a physiological reaction in basic memory and focus skills for young children, and is more damaging in the school setting than at the home.

Viewpoint Vancouver has also been writing about the health challenges of traffic in terms of asthma and breathing conditions, including the death of a student in London directly linked to vehicular carbon emissions.

It just makes sense to ensure that young children who inhale higher concentrations of pollution due to their smaller size, smaller lungs and more rapid breathing rate have the least exposure possible to particulate matter (PM). Walking to school because of their small size they are closer to exhaust level height, and  closeness to major roads elevates TRAP (traffic related pollutant)  levels in children.

This new study published at  and done from Lancaster University shows that surrounding schools with greenery like trees and hedges can greatly reduce pollutants by  nearly 50 percent.

The research was done at three Manchester Great Britain primary schools and looked at “tredges”, trees managed as a two meter hedge.

The research indicates that the species of hedging is most important to ensure pollutant capture and mitigation, and shows that the western red cedar “tredge” reduced black carbon (BC) and particulate matter. The study showed in testing in school yards and playgrounds that vegetation installed at the perimeter of schools on the road side significantly captured pollution deposits on the leaves of the shrubs.


This is in keeping with a study that Viewpoint Vancouver wrote about last year showing that hedges along roadways planted with  cotoneaster (cotoneaster franchetti) also can soak up vehicle emitting pollution. As the study said:

“On major city roads with heavy traffic we’ve found that the species with more complex denser canopies, rough and hairy-leaves such as cotoneaster were the most effective. We know that in just seven days a one metre length of well-managed dense hedge will mop up the same amount of pollution that a car emits over a 500 mile drive.”

Here is why this is important: fine particulate matter exposure  caused by air pollution causes six to nine million deaths annually. This research shows that the use of “tredges” that filter and capture particulate can be used in other urban areas besides schools to reducedamaging health impacts of exposure to traffic pollution”.






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