The Mayor's Ambient Noise Strategy - Greater London Authority

72 Mayor of London
The Mayor’s Ambient Noise Strategy
perhaps 10 metres to have any real effect. Issues of space and personal
safety need to be considered. However, narrower belts of dense
vegetation - or even just street tree planting - can subjectively improve
people’s perceptions. Trees and other vegetation can make other forms of
noise screening more visually acceptable. The amenity, cooling and other
benefits to be gained from tree planting reinforce their role.
4A.27 Noise barriers need to be as close as possible to the source, or to the
receptor. Roadside barriers need to be continuous over long distances to be
effective. Lack of space and frequent junctions make effective barriers
impractical on most London roads. Badly-designed barriers can sever
communities, attract graffiti, block views, and make people feel less safe. In
London, many properties would be too close to the street, or too high, to
be effectively screened. However, even if barriers would not reduce noise
suffiently at windows of noise sensitive properties, there might still be some
benefits for gardens and other open areas. Theoretical performance may not
be achieved in urban areas with multiple noise reflections among buildings.
There is at present no specific funding for developing noise barriers.
Support from adjacent development could be an option.
4A.28 Low barriers can, however, be effective on elevated roads and flyovers.
One type of safety parapet which screens noise may not cost more than
another which does not. Sound absorbing surfaces on highway structures,
such as vertical cutting walls, within tunnel mouths, or on supporting
surfaces of elevated structures could reduce noise, and may be more costeffective
during refurbishment.
4A.29 In other European countries, more ambitious noise barriers have been
installed. Many different materials and imaginative designs have been
used. To be effective, urban noise barriers often need to be taller than a
typical wooden fence or garden wall. Their length means they become
dominant features in the urban landscape. Continental practice
demonstrates that successful environments can be achieved where skilled
designers make strong urban design statements. By contrast, an apologetic
‘keeping in keeping’ approach can make urban surroundings cumulatively
less interesting. Attractive solutions can, however, be expensive,
particularly those that involve cantilevering a barrier partially over the
road. Combining noise barriers with generation of electricity using
photovoltaics (see glossary) may be feasible. 14 Their performance can
deteriorate if they are not well-maintained, and they should meet relevant
guidance and standards. 15 The screening performance of noise barriers can
fall considerably after installation. The quality of the original construction
is at least as important as age. Regular checks need to be considered.