The Mayor's Ambient Noise Strategy - Greater London Authority

The Mayor’s Ambient Noise Strategy Mayor of London 135
seek, as far as practicable and appropriate, to take account of likely
changes in the levels of road, rail and aircraft noise. Studies should assess
how housing needs can best be met while minimising noise exposure.
Box 45: Planning Policy Guidance Note 24, and
Building Bulletin 93: Schools
PPG24 regards 60 dBL Aeq
as a desirable upper limit for major new noisesensitive
development exposed to aircraft noise. It states that ‘When
determining applications to replace schools and build new ones in such
areas, local planning authorities should have regard to the likely pattern
of aircraft movements at the aerodrome in question which could cause
noise exposure during normal school hours/days to be significantly higher
or lower than shown in average noise contours’. More recent guidance in
the Department for Education and Skills (DfES) Building Bulletin 93 30
suggests that noise should be assessed by taking the highest L Aeq
values
likely to occur in any 30 minute period during normal teaching hours and
that, for aircraft flyovers, the highest 30 minute value of L A1
(the level
exceeded for 1% of the 30 minute period) should also be considered for
many types of teaching room. (See also Appendix A5, including review of
planning policy guidance)
Box 46: Worst mode
Some have argued that ‘worst mode contour’ (see glossary) should be
used for planning and development control purposes, rather than ‘average
mode’. Although easterly take-off may, in an average year at Heathrow,
for example, occur only on one day in five, it may be argued that
development should be planned and designed on the basis of aircraft
noise contours for that ‘worst mode’ condition. In the case of schools to
the east of Heathrow, for example, easterly operations may, in practice,
predominate during a substantial period. This could mean that a period
important for child learning could be subject to noise at a higher than
‘average’ level. This factor is implicitly recognised in Building Bulletin 93
(see box above), but there is no equivalent advice for other noise
sensitive buildings. This issue needs to be considered in reviewing
Planning Policy Guidance Note 24, and against the background of
European moves towards annual noise values.
4C.37 The time period over which aircraft noise should be assessed is an issue of
particular importance for schools (see boxes above). Schools can be
affected not just by aircraft, road, railway or other external noise, but by
high levels of ‘cross-talk’ between different activities within the school.
Issues are considered in paragraphs 4F.14-17 in Chapter 4F. While
comprehensive information is not available, it is likely that the acoustic
environment in many school buildings in London is less than satisfactory