Air quality strategy - Policy 10, low-level hedges

MQT on 2009-11-18
Session date: 
November 18, 2009
Question By: 
Mike Tuffrey
Liberal Democrats
Asked Of: 
The Mayor


One of the proposals in your draft Air Quality Strategy is to 'Work with boroughs to investigate the planting of low-level hedges along major roads where air quality is poor, to act as a barrier between emissions from road transport and pedestrians on pavements'. Where have such hedges been proven to work? What impact would they have on concentrations? How much would they cost, and how cost effective would they be?


Answer for Air quality strategy - Policy 10, low-level hedges

Answer for Air quality strategy - Policy 10, low-level hedges

Answered By: 
The Mayor

TfL is developing tailored packages of measures for the few locations in central London that are at risk of not meeting targets for PM10 in 2011. The packages will be based on the characteristics of the particular site, including the vehicle fleet using the roads, traffic speeds and local geography. Planting trees and hedges, such as low level hedges, is likely to be just a small part of those packages, which could also include changes in traffic management, altered street design and focusing cleaner buses on routes going though these locations.

Examples of vegetation planting schemes have been trialled in Beijing, New York and the Netherlands.

As yet we do not know the exact impacts tree and low-level hedge planting will have in London. The costs of planting street trees under the Mayor's street tree programme is around £350 per tree, however this can be higher depending on the local circumstances. Trialling the technique will help us gain a far better understanding of the costs and the effectiveness of different types of vegetation as a mitigation measure.