New Delhi :Researchers from the University of Surrey including one of Indian origin in the UK have found planting 
roadside hedges, rather than just relying on trees, can most effectively reduce pollution exposure from cars in near-road environments.
They found that roadsides that only had hedges were the most effective at reducing pollution exposure, cutting black carbon by up to 63 per cent. Ultrafine and sub-micron particles followed this reduction trend, with fine particles showing the least reduction among all the measured pollutants.
The study, published in the journal ‘Atmospheric Environment’, used six roadside locations in the UK as test sites where the green infrastructure was between one to two metres away from the road.
The maximum reduction in concentrations was observed when the winds were parallel to the road due to a sweeping effect, followed by winds across the road.
Roadsides with only trees showed no positive influence on pollution reduction at breathing height as the tree canopy was too high to provide a filtering effect for road-level tailpipe emissions