Car exhaust emissions react with sunlight and heat to cause polluting gases such as tropospheric ozone. This is the main ingredient of poor air quality and photo-chemical smog, which can cause breathing difficulties. To find out the level of ozone pollution across Europe, go to EEA's Live Ozone Map.
Let the grass grow higher and thus encourage root growth. It will also allow the grass to self-seed. If you mow a path in the middle, it will show that it is indeed meant to be that way as opposed to being neglected.
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