The Mayor's Ambient Noise Strategy - Greater London Authority

104 Mayor of London
The Mayor’s Ambient Noise Strategy
especially at night. Otherwise, acceleration and deceleration rates should
be minimised. Heavy diesel engines should not be kept idling, emitting
low frequency noise which people can find particularly annoying. Network
Rail has an agreement with the largest rail freight operating company,
EWS, that signallers will inform drivers if they will be waiting for more
than 15 minutes, so that the driver can shut down the locomotive. The
signaller informs the driver 5 minutes before a green signal. A similar
approach is sought in stations, but powers are not available to enforce the
practice in either case. Railway horns and other warning devices can
disturb or startle waiting passengers and those living close to railways.
Alternative ways of achieving safety objectives should be periodically
reviewed by the railway industry. Where audible signals are unavoidable,
ways of reducing adverse impacts, such as using broadband sound, or
otherwise improving sound quality, should be considered.
policy 20
The Mayor will urge the Strategic Rail Authority and the rail industry to
promote the cost-effective development and adoption of quieter railway
vehicle technologies and management systems. Railway operating
practices which minimise noise, particularly at night, should be promoted
and ‘no idling’ policies observed.
Railway structures and noise barriers
4B.15 Vibration of steel bridges and other structures can radiate noise. This can
be complex and expensive to reduce, but options should be examined
when structures, particularly long spans, are being refurbished or
replaced. Many bridges and viaducts incorporate a parapet which may act
as a noise barrier, screening wheel-rail noise for buildings of moderate
height. Noise barriers can be structurally difficult to achieve on viaducts
at low cost. Parapets can also re-radiate sound resulting from vibration in
the bridge structure, negating the shielding effect of the parapet. It may
require comprehensive isolation of the track from the viaduct to avoid
this, although this could only be done as a part of a major track
replacement programme. Options to improve parapet screening could be
most cost-effective where replacement, or other major works occur.
4B.16 Railway cuttings can screen noise, although they are less effective for low
frequency noise. Noise from cuttings can be reduced by using absorptive
surfaces on vertical retaining walls, and inside the mouths of tunnels,
where clearances allow. In ‘natural’ cuttings, sloping rough ground can
attenuate sound. Dense vegetation may assist if the width is several
metres. Barriers close to tracks are most effective, but are subject to
safety and other operational constraints. Well-placed, well-designed
barriers can reduce rolling noise by over 10 dB. They are less effective
against diesel locomotives on power, where the main source of the noise