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3 ROAD TRAFFIC NOISE ASSESSMENT
3.1 Traffic Noise Criteria
Road traffic noise impacts addressed in this report are assessed in accordance with the NSW
Environmental Criteria for Road Traffic Noise (ECRTN, NSW Environment Protection Authority
1999) and the RTA’s Environmental Noise Management Manual (ENMM, 2001). The Central
Coast Highway is classed as an arterial road in that it handles through traffic bound for another
locality and has characteristically heavy and continuous traffic flows.
This project involves upgrading the existing arterial road to incorporate a dual carriageway.
According to the ENMM, this project does not constitute a ‘new road traffic noise source’
because the road is not a new road and does not produce noise to receptors from a different
direction. This project is essentially an expansion of an existing arterial road to increase traffic
carrying capacity and there is already an existing road traffic noise exposure greater than
55dB(A) LAeq(15hr) and/or 50dB(A) LAeq(9hr). Therefore, the “redeveloped road” criteria as set out
in the ECRTN apply. The noise criteria for redevelopment of an existing arterial road are as
follows.
Table 3.1 - NSW Environmental Criteria for Road Traffic Noise
Criteria, dB(A) Type of Development Day Night
Where Criteria are Already Exceeded
3. Redevelopment of existing freeway/arterial road
LAeq(15hr) 60 LAeq(9hr) 55 In all cases, the redevelopment should be designed so as not to increase existing noise levels by more than 2 dB.
Where feasible and reasonable, noise levels from existing roads should be reduced to meet the noise criteria. In many instances this may be achievable only through long-term strategies such as improved planning, design and construction of adjoining land use developments; reduced vehicle emission levels through new vehicle standards and regulations of in-service vehicles; greater use of public transport; and alternative methods of freight haulage
Sensitive Land Use Developments
The ECRTN also sets guidelines for the assessment of traffic noise on sensitive land uses such
as schools, hospitals, places of worship and recreation areas. There are no sensitive land uses
within the study area, thus noise goals are not required to be set for these types of
developments.
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3.2 Traffic Flow and Composition Summary
3.2.1 Existing Traffic Volumes along the Central Coast Highway
A traffic survey was undertaken by Austraffic along the Central Coast Highway between
Matcham Road and Ocean View Drive. This survey was performed between Friday 27 June to
Friday 4 July 2008. Traffic counts were undertaken at two locations, between Matcham Rd and
Willoughby Rd and between Willoughby Rd and Ocean View Drive. The following tables show
traffic volumes and compositions of those two sections, in terms of daytime (15hr) and night-
time (9hr) data, averaged over the seven day measurement period.
Table 3.2 – Traffic volumes along the Central Coast Highway – 2008
Eastbound Westbound
Road Section Period Volume
Per Cent Heavy
Volume Per Cent Heavy
Day: 7am – 10pm 9,889 4 9,517 4 Central Coast Highway between Matcham Rd and Willoughby Rd Night: 10pm – 7am 666 5 1,175 5
Day: 7am – 10pm 8,676 4 8,817 3 Central Coast Highway between Willoughby Rd and Ocean View Dr Night: 10pm – 7am 692 5 1,068 4
3.2.2 Existing Traffic Volumes on Roads Adjoining the Central Coast Highway
Existing traffic volume data for roads adjoining the Central Coast Highway was provided from a
2006 study conducted by Northern Transport Planning and Engineering Pty Ltd (NTPE).
These traffic volumes are considered representative of the existing situation, as traffic volumes
along this section of the Central Coast Highway have not increased significantly since 2006.
Heavy vehicle percents range from 1% up to 9%.
Table 3.3 – Traffic volumes on roads adjoining the Central Coast Highway – 2006
Road Period Northbound Volume Southbound Volume
Day: 7am – 10pm 1,075 728 Matcham Rd
Night: 10pm – 7am 111 79
Day: 7am – 10pm 1,263 1,642 Willoughby Rd
Night: 10pm – 7am 180 166
Day: 7am – 10pm 749 636 Old Gosford Rd
Night: 10pm – 7am 82 130
The traffic data presented in Sections 3.2.1 and 3.2.2 were used in model verification (see
Section 3.3.2 below).
3.2.3 Future Traffic Volumes along the Central Coast Highway
Future traffic volume data for the Central Coast Highway was provided by Parsons Brinckerhoff
and is summarised in Table 3.4 and 3.5 below.
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2012 volumes are for the “future-existing” scenario (do nothing option at project opening).
Table 3.4 – Traffic volumes along the Central Coast Highway – 2012
Eastbound Westbound
Road Section Period Volume
Per Cent Heavy
Volume Per Cent Heavy
Day: 7am – 10pm 10,027 4.9 9,977 3.8 Central Coast Highway between Matcham Rd and Willoughby Rd Night: 10pm – 7am 683 6.7 1349 4.7
Day: 7am – 10pm 11,399 4.3 10,868 3.5 Central Coast Highway between Willoughby Rd and Ocean View Dr Night: 10pm – 7am 776 5.8 1,470 4.3
Table 3.5 – Traffic volumes along the Central Coast Highway – 2022
Eastbound Westbound
Road Section Period Volume
Per Cent Heavy
Volume Per Cent Heavy
Day: 7am – 10pm 12,306 4.9 12,245 3.8 Central Coast Highway between Matcham Rd and Willoughby Rd Night: 10pm – 7am 838 6.6 1,656 4.7
Day: 7am – 10pm 13,989 4.3 13,338 3.5 Central Coast Highway between Willoughby Rd and Ocean View Dr Night: 10pm – 7am 953 5.8 1,804 4.3
3.2.4 Future Traffic Volumes on Roads Adjoining the Central Coast Highway
Future traffic volume data for roads adjoining the Central Coast Highway was provided by
Parsons Brinckerhoff and is summarised in Table 3.6 and 3.7 below. Heavy vehicle percents
range from 1% up to 9%.
2012 volumes are for the “future-existing” scenario (do nothing option at project opening).
Table 3.6 – Traffic volumes on roads adjoining the Central Coast Highway – 2012
Road Period Northbound or
Westbound Volume Southbound or
Eastbound Volume
Day: 7am – 10pm 1,680 2,025 Willoughby Rd
Night: 10pm – 7am 170 205
Day: 7am – 10pm 845 1,044 Old Gosford Rd
Night: 10pm – 7am 85 106
Day: 7am – 10pm 118 95 O’Kanagan Close
Night: 10pm – 7am 12 10
Day: 7am – 10pm 7,674 8,400 Ocean View Drive
Night: 10pm – 7am 776 850
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Table 3.7 – Traffic volumes on roads adjoining the Central Coast Highway – 2022
Road Period Northbound or
Westbound Volume Southbound or
Eastbound Volume
Day: 7am – 10pm 1,834 2,243 Willoughby Rd
Night: 10pm – 7am 186 227
Day: 7am – 10pm 926 1,144 Old Gosford Rd
Night: 10pm – 7am 94 116
Day: 7am – 10pm 118 100 O’Kanagan Close
Night: 10pm – 7am 12 10
Day: 7am – 10pm 8,436 9,254 Ocean View Drive
Night: 10pm – 7am 854 936
The traffic data presented in Sections 3.2.3 and 3.2.4 were used to model future traffic noise
levels along the Central Coast Highway (see Section 3).
3.3 Noise Prediction Modelling
3.3.1 Noise Prediction Model
The traffic noise prediction model used in this project is based on a method developed by the
United Kingdom Department of Environment entitled “Calculation of Road Traffic Noise (1988)”
known as the CoRTN (1988) method. This method has been adapted to Australian conditions
and extensively tested by the Australian Road Research Board. The model predicts noise levels
for free-flowing traffic and a modified method has been developed which enables an accurate
prediction of noise from high truck exhausts to be taken into account. The method predicts the
L10(1hour) noise levels, and a correction of -3dB(A) is applied to obtain the Leq(1hour) noise levels
for every hour in a 24 hour day.
The Leq(1hour) noise levels for the time period 7.00am to 10.00pm are then collated and
logarithmically averaged to derive the daily Leq(15hour) noise level. Similarly, the Leq(1hour) noise
levels for the time period 10.00pm to 7.00am are collated and logarithmically averaged to
derive the night time Leq(9hour) noise level.
Traffic volumes used in modelling are detailed in Section 3.2.
Distances between vehicles and critical receivers were obtained from site measurements and
from drawings supplied by Parsons Brinckerhoff and the RTA.
The noise prediction model takes into account the following:
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Table 3.8 – Summary of Modelling Inputs
Input Parameters Data Acquired From
Traffic volumes and mix Existing: Traffic counts from Austraffic and NTPE
Future: Provided by Parsons Brinckerhoff. Described in more detail in Section 3.2 of the Review of Environmental Factors (REF)
Vehicle speed Central Coast Highway: Posted speed limit of the proposed upgrade will be 60km/h; noise modelling was done for 70km/h as a precautionary measure.
Side Roads: 50km/h
Current speed limits observed during site inspection. Speeds to remain the same through to 2022.
Gradient of roadway From the Proposal as described in Section 3 of the REF
Source height 0.5m for car exhaust, 1.5m for car and truck engines and 3.6m for truck exhaust and detailed within CoRTN88
Ground topography at receiver and road From aerial photos, digital topographic data and the Proposal as described in Section 3 of the REF
Angles of view from receiver Determined during site inspections and aerial photos
Reflections from existing barriers, structures and cuttings on opposite side of road
Determined during site inspections and review of concept design.
Air and ground absorption Detailed within CoRTN88, ground absorption varied along route. Numeric values varied between 0 (hard surface) to 1 (100% absorptive)
Receiver Heights 1.5m above ground level for ground floor and 4.5m above ground level for 1st floor
Facade correction +2.5dB(A)
Acoustic properties of road surfaces Determined during site inspection – dense graded asphalt
Roadside barriers Existing fencing at properties
Prediction model assumes no existing noise walls
Traffic noise levels (LAeq) Based on long term monitoring results
3.3.2 Model Verification
The model was verified and calibrated using the long-term noise monitoring results obtained for
this project.
Table 3.9 summarises the results of the traffic noise model verification, providing a
comparison of the modelled traffic noise levels for existing conditions compared to the
measured traffic noise levels.
Table 3.9 – Noise Model Verification Results
LAeq(15hr) Noise Level LAeq(9hr) Noise Level NCA
Measured Modelled Variation Measured Modelled Variation
1 58 611 +3 52 531 +1
2 52 53 +1 47 46 -1
3 61 63 +2 55 56 +1
4 57 58 +1 52 51 -1
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LAeq(15hr) Noise Level LAeq(9hr) Noise Level NCA
Measured Modelled Variation Measured Modelled Variation
5 65 64 -1 60 57 -3
Notes: 1. Includes a -3.6dB correction factor to account for specific characteristics of the M1 measurement location. These characteristics included significant vegetation and partial shielding from the residential building itself.
Variations between measured and modelled noise levels are likely to have occurred due to
differences in actual vehicle numbers, percentages of heavy vehicles, vehicle speeds and
topographic data used in the model compared to actual levels.
The noise model verification tests presented in Table 3.9 above, show the model to predict
results that fall within ± 3dB(A) of the true noise levels in practice. The accuracy of the
CoRTN88 noise algorithms is generally expected to predict noise levels that are within 2.7dB(A)
of the true noise levels in practice with an 85% confidence [RTA’s Interim Traffic Noise Policy
(ITNP), Appendix B, Section 3]. Therefore, the results presented above provide a reasonable
level of confidence in the accuracy of the noise model used for predicting future traffic noise
levels for this project.
The variations listed in the table above were used as ‘calibration factors’ applied to the
predicted traffic noise levels on a catchment by catchment basis.
3.4 Road Traffic Noise Assessment
3.4.1 Prediction Locations
Road traffic noise levels were predicted to all residences within each NCA using noise contour
maps. In addition, further noise modelling was completed at each individual residence.
The noise contours were interpolated from a series of calculations to specific points within a
regularly spaced grid, 1.5 m above ground level. It is noted that the noise contours are
estimates of the predicted noise levels, and that contour values may differ slightly from
equivalent calculations at individual residences.
For calculations at individual residences, all residential buildings were assumed to be single
storey, unless the building height was over 4.5 m (determined from building survey data
provided). Residential buildings over 4.5 m in height were assumed to be double storey
dwellings, in line with a conservative assessment.
Predictions were carried out assuming no noise control measures have been incorporated into
the road development other than those measures detailed in Table 3.8.
Review of predicted noise levels at the nominated, nearest affected residential receivers in each
NCA revealed that noise impacts were generally higher during the day. Therefore, the day
period is the determining period for assessment purposes. Traffic noise levels presented in
Figures 2 through 13 are for ground floor level only.
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The future-existing noise levels are the predicted traffic noise levels in year 2012 if the road
upgrade was not to be carried out. The future noise level in 2012 is the predicted traffic noise
level in the year the proposed works are complete and the redeveloped road commences
operation, while the year 2022, represents ten years after the commencement of operation.
Date: 09/09/08
Scale: NTS
Ref: TD780-01P02 (rev 0)
Title :
Figure 2 - 2012 Future Existing day contours - 1.5m
Project :
Central Coast Highway Upgrade -
Matcham Road to Ocean View Drive
CAAA Member of the Association of Australian Acoustical Consultants
Consultants in Acoustics, Vibration and Structural Dynamics
RENZO TONIN& A S S O C I A T E S
Email: [email protected] www.renzotonin.com.au
SydneyPh: (02) 8218 0500 Fax: (02) 8218 0501MelbournePh: (03) 9606 0041 Fax: (03) 9606 0042BrisbanePh: (07) 3211 9155 Fax: (07) 3211 9188Gold CoastPh: (07) 5593 5633 Fax: (07) 5593 5635KuwaitPh: +0011 965 653 1520
inspired to achieve
N
60
6065
65
55
50
50
55
50
45
Central Coast Highway
Bru
sh
Ro
ad
Matc
ham
Road
Brooks Hill Lane
NOTES
65dBA
60dBA
55dBA
50dBA
45dBA
Date: 09/09/08
Scale: NTS
Ref: TD780-01P03 (rev 0)
Title :
Figure 3 - 2012 Future Existing day contours - 1.5m
Project :
Central Coast Highway Upgrade -
Matcham Road to Ocean View Drive
CAAA Member of the Association of Australian Acoustical Consultants
Consultants in Acoustics, Vibration and Structural Dynamics
RENZO TONIN& A S S O C I A T E S
Email: [email protected] www.renzotonin.com.au
SydneyPh: (02) 8218 0500 Fax: (02) 8218 0501MelbournePh: (03) 9606 0041 Fax: (03) 9606 0042BrisbanePh: (07) 3211 9155 Fax: (07) 3211 9188Gold CoastPh: (07) 5593 5633 Fax: (07) 5593 5635KuwaitPh: +0011 965 653 1520
inspired to achieve
N
50
55
55
60
6065
45
O'K
anagan C
lose
Central Coast Highway
Old Gosford Road
OceanViewDrive
Will
oughby R
oad
Hig
hV
alley
Clo
se
NOTES
65dBA
60dBA
55dBA
50dBA
45dBA