Inquiry Note in Relation to Proposed Planning Condition 10
Introduction
1. The proposed planning conditions for the Order1, includes the following with regards to
ground-borne noise from the tramway:
“Ground Borne Noise
10. Where the dominant source of noise is ground-borne, the following noise standards shall
be applied to the development for the application of Sections 6 and 7 of the Noise and
Vibration Policy:
(i)
Inside noise sensitive rooms in residential buildings – LAmax,S40dB; and
(ii)
Inside noise sensitive rooms in offices – LAmax,S45dB
Reason: In order to safeguard the amenities of occupiers of premises/dwellings in the vicinity
from ground-borne noise and vibration caused by the running of trams in accordance with
Paragraphs 3.8 and 3.10 of the Birmingham UDP 2005 and the National Planning Policy
Framework 2012.” [Paragraphs 3.8 and 3.10 of the UDP are reproduced as Annex 1 of this
Note.]
2. The purpose of this Inquiry Note is to explain the rationale behind the proposed condition.
Background
3. The proposed planning condition is identical to Planning Condition 11 that was attached to
the planning permission for the Birmingham City Centre Extension (BCCE) dated 1 July 2005
except the reason given for the latter was given as “To minimise impact from ground-borne
noise and vibration caused by the running of trams.”
1
Winckworth Sherwood LLP, 2013. The Midland Metro (Birmingham City Centre Extension Land Acquisition
and Variation) Order. Rule 10(6) Request for Planning Permission. Schedule 1 Proposed Planning Conditions.
Overview of Ground Borne Noise from Railways
4. The movement of railway vehicles generates ground-borne vibration due to the roughness
of the running surfaces in contact between the wheels and the rails. This generates
fluctuating contact forces which are transmitted into the track and supporting structure or
ground. Where the vibration is transmitted via the ground into buildings, the building
elements such as the walls and floors can respond by radiating noise at frequencies that are
audible. This can be perceived as a rumbling sound and is typically in the 16 Hz to 250 Hz
frequency range.
5. Ground-borne noise is often more easily perceived in the case of underground railways
where the contribution from sources of airborne noise does not reach the receptor. For
surface railways, the contribution of airborne noise is normally the dominant type of noise
impact affecting sensitive receptors adjacent to the track.
6. It is conventional to describe ground-borne noise from railways by quantifying the highest
part of the sound event during the passage of a train using the maximum A-weighted
maximum sound pressure level in decibels using the slow time-weighting denoted LAmax,S.
Criteria
Residential Buildings
7. The UK Tram Phase 2 report published by the UK Tram ‘Activity Group 4 Operational Noise
and Vibration’ project2 represents current best practice for the management of operational
noise and vibration from tramways within the UK.
8. Section 13.3 of the Phase 2 states the following with regards to 40 dB(A) criterion applied in
the case of occupied properties adjacent to the tramway:
“For ground-borne noise (rumble), the use of a limit of 40 dB(A) measured on a meter with
“Slow” response for any individual tram pass-by event is based on American Public Transit
Association Guidelines from 1981, and has subsequently been applied successfully to a
number of UK rail schemes (eg the Channel Tunnel Rail Link tunnels, Jubilee Line Extension,
Crossrail, Croydon Trams). Its continued application is therefore recommended.”
9. Clause H.4 of BS 8233:20143 concerns internal noise levels affecting hotels due external
sources of noise, based on the design criteria adopted by hotel groups. It states:
2
UK Tram Ltd, 2007. Support to UK Tram Activity 4 Operational Noise and Vibration Phase 2 Reports.
British Standards Institution, 2014. BS 8233:2014 Guidance on sound insulation and noise reduction for
buildings.
3
“The noise level in any hotel bedroom, with windows closed, from all external sources,
including road, rail and air traffic and noise from activities outside the hotel and any adjacent
premises, are to be within the range of average noise levels…Night-time (23.00 – 07.00 hrs)
45 – 55 dB LAmax”. The time-weighting function (e.g. fast or slow) is not specified. Section 6.3
of BS ISO 14387-1:20054 states:
“All other parameters remaining equal, LPAFmax with a fast time constant will be
approximately 1 dB to 2 dB greater than LPASmax for rail systems using continuously welded
rail, and 3 dB to 4 dB greater for jointed rail.” [The parameter ‘LPASmax’ is the same as ‘LAmax,S’
but is expressed using a slightly different convention for notation.]
10. Therefore, even if the BS 8233 criterion of 45 dB LAmax is evaluated using the fast time
weighting then the equivalent value using the slow time-weighting, obtained by this
approximation, is greater than 40 dB(A) in the worst case.
11. It is concluded that the LAmax,S 40 dB criterion is appropriate for residential buildings and, if
applied in the case of the Hyatt Regency on Broad Street, would be more stringent than the
minimum design criterion for hotels referenced in BS 8233:2014.
Offices
12. There are no widely adopted ground-borne noise criteria that are specifically applicable to
offices. BS 8233:2014 presents various design targets for offices but in terms of values
described as an A-weighted equivalent continuous sound level (LAeq). These cannot be
directly compared to the criterion expressed in terms of LAmax,S.
13. However, it is expected that any requirement for offices would be less stringent than one
applicable to buildings where people normally sleep. On this basis, a criterion of LAmax,S 45dB
is considered to be appropriate for ground-borne noise impacts from the operation of the
tramway affecting sensitive rooms in offices.
4
British Standards Institution, 2005. BS ISO 14387 Mechanical vibration – Ground-borne noise and vibration
arising from rail systems – Part 1: General guidance.
Conclusion
14. This Inquiry Note has reviewed the proposed Planning Condition 10 for the Order, which
specifies limits on ground-borne noise impacts affecting noise sensitive rooms inside
residential buildings and offices.
15. The criteria given in the proposed planning condition are consistent with those of Planning
Condition 11, which was attached to planning permission for the BCCE dated 1 July 2005.
The track-form of the CSQ extension will be designed and installed to ensure compliance
with the criteria within the condition.
16. The LAmax,S 40 dB criterion for noise sensitive rooms within residential buildings is consistent
with the recommendations of the best practice guidance published by UKTram and a
number of large UK rail projects. It is considered to be an appropriate criterion applied in the
case of sensitive rooms inside residential buildings. The application of the criterion in the
case of the Hyatt Regency Hotel on Broad Street is also considered appropriate as it is more
stringent the minimum design criterion for hotels referenced in BS 8233:2014.
17. The LAmax,S 45 dB criterion given in the proposed planning condition for noise sensitive
rooms within offices cannot be directly compared to the design targets given in
BS 8233:2014 for various offices types. However, the criterion is considered to be
appropriate.
Andrew Monk-Steel
Principal Acoustic Engineer, Mott MacDonald
Monday 1 December 2014
Annex 1 – Extracts of the Birmingham UDP 2005
The paragraphs of the Birmingham UDP 2005 referenced in the reason for the proposed planning
condition are as follows:
“3.8 The environment strategy is based on two principles:(a) the need to protect and enhance what is good in the City’s environment, and to improve
what is less good;
(b) the need to recognise the key relationship between environmental quality and levels of
economic activity.
The keynote must be quality. This will require a continuation of the wide range of current
initiatives - derelict land clearance, residential and environmental
improvement schemes, both in the City Centre and in the suburbs, canal enhancement, City
Centre pedestrianisation etc - and no doubt the development of new approaches to new
problems. Where appropriate, these will be secured through planning obligations that are
directly, fairly and reasonably related in scale and kind to the proposed
development. Some of these initiatives are discussed in more detail in other sections of the
UDP. The function of this section is to provide the overall policy context within which they
will all find their place.”
“3.10 Proposals which would have an adverse effect on the quality of the built environment
will not normally be allowed.”
Annex 2 – Midland Metro Extension – Noise and Vibration Policy October 2003
MIDLAND METRO EXTENSIONS - NOISE AND VIBRATION POLICY
OCTOBER 2003
MISSION STATEMENT
1.
Centro is committed to maintaining a harmonious environment that contributes
towards sustainable development through considering environmental, social,
ethical and community factors in addition to economic and engineering viability.
Part of this commitment is to adopt and continually reflect best practice in
controlling noise and vibration impact assessment.
2.
INTRODUCTION
Through its experience of operating Line 1 of the Midland Metro Centro has gained an
understanding of the noise and vibration that is generated by their light rail system. Centro
will use this experience in planning and operating extensions to the system so as to
minimise disturbance.
This Noise and Vibration Policy addresses the operation of future extensions to the Midland
Metro system. Impacts during construction are covered in the Code of Construction
Practice.
3.
STANDARDS AND GUIDELINES
Centro commit to adopting:•
•
•
the guiding principles set out in Planning Policy Guidance Note 24, Planning and
Noise (PPG24);
The Noise Insulation (Railways and other Guided Transport Systems) Regulations
1996; and
other best guidance as seen 'fit for purpose'.
Centro will adopt appropriate noise and vibration emission standards in their
procurement of new Metro vehicles.
4.
NOISE INSULATION REGULATIONS
Noise insulation is mandatory for residential properties in accordance with the Noise
Insulation Regulations at the qualifying façade levels:
• 68 dB LAeq, 0600 – 0000 hours daytime; and
• 63 dB LAeq, 0000 - 0600 hours night.
A further qualifying free-field level of LAmax, slow 82 dB several times an hour at night (23000700 hours) will apply for the purposes of avoiding sleep disturbance where at source
mitigation measures are not practicable.
For insulation to be offered tram noise must increase the corresponding ambient noise level
by at least 1dB(A).
5
NOISE MITIGATION AT SOURCE
There is no statutory requirement for mitigation at levels below the Noise Insulation
Regulations standards (see below). However, consideration will be given to developing
mitigation measures at lower noise levels where significant impacts are predicted and where
it is reasonable and appropriate to do so. Mitigation will be considered for noise sensitive
receivers including all types of dwellings, schools, libraries, hospitals, and places of worship.
Buildings housing particularly sensitive activities, such as those used for musical
performances, may require special attention.
The threshold above which noise mitigation will be considered is taken as the free-field
noise levels at the top of Noise Exposure Category A from PPG24; ie
LAeq 0700-2300 hours 55 dB;
LAeq 2300-0700 hours 45 dB.
In line with current guidance 3dB (A) is taken as the limit to the perception of change in
environmental noise.
Where tram noise is perceptibly above these thresholds (ie by at least 3 dB) mitigation
measures to reduce the adverse impact of noise intrusion shall be implemented using Best
Practicable Means depending on the extent to which pre-existing ambient (LAeq, 1 hour) noise
levels are increased, under the following criteria:
Increase of less than 3dB No mitigation required
Increase of more than 5dB
Mitigation considered on a case by case
basis with increasing priority for greater
noise increase
Mitigation will usually take the form of trackside noise bunds, noise barriers or track
treatments. Noise bunds and barriers will not always be suitable for various reasons such as
conflicts with road traffic, concerns of track safety, driver sight lines, visual impact, security
and crime considerations, and construction and maintenance issues. In each case noise
mitigation will be considered on the basis of a value judgement.
6.
VIBRATION
Trackforms will be designed adjacent to sensitive receptor buildings using Best Practicable
Means to keep within the guideline levels of Vibration Dose Value (VDV) given in BS6472,
1992 below which the probability of adverse comments is low:
•
•
Day (0700-2300 hours) 0.4 m/s1.75; and
Night (2300-0700 hours) 0.13 m/s1.75.
7.
MONITORING AND MAINTENANCE
Centro is committed to maintaining the system, and in particular the wheel and rail surfaces,
so as to minimise noise and vibration at sensitive receptors. For each extension an
appropriate noise and vibration monitoring scheme will be agreed with the relevant local
authorities. The results will be used to inform wheel and track maintenance programmes in
order to ensure unnecessary increases in noise or vibration are avoided.
Centro will give due notice to local authorities and affected residents of plans to carry out
potentially noisy maintenance activities such as rail grinding.