Road Traffic Noise. Warrandyte Road. North Ringwood, South Warrandyte & Park Orchards Tortice Drive to Falconer Road

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1 Road Traffic Noise Warrandyte Road North Ringwood, South Warrandyte & Park Orchards Tortice Drive to Falconer Road Prepared by Stephen Spicer & Associates Pty Ltd ACN: January 7, 2008

2 INDEX 1 INTRODUCTION 3 2 MEASUREMENT TECHNIQUE 4 3 MEASUREMENTS Test Point Test Point Test Point Comparative Summary Asphalt Textures At Each Test Site Friction Coarse Asphalt / Open Graded Asphalt Equivalent Traffic Volume 7 4 CONCLUSIONS 8 5 APPENDIX Equivalent Traffic Volume Asphalt Classification to AS REFERENCES & ATTACHMENTS 10

3 1 Introduction This report compares the noise levels produced at various locations along Warrandyte Road, between Tortice Drive and Falconer Road (North Ringwood, South Warrandyte and Park Orchards). Different types of asphalt, with differing surface texture, are used along this section of Warrandyte Road. The focus of this report is to evaluate the difference in noise levels between the different types of asphalt, and to make recommendations to reduce noise levels over the section of road concerned The map below highlights the relevant section of Warrandyte Road. Figure 1: The section of Warrandyte Road investigated.

4 2 Measurement Technique The Sound Pressure Level (SPL) was measured with a Rion Sound Level Meter (SLM), using a statistical pass-by method. The measurements were made using A-weighting characteristic. Microphone location was compliant with recommendations in Australian Standard AS2702 (Ref. 1): Microphone height. 1.2m ±0.05 m above the ground surface Horizontal distance from microphone. The microphone was 6 m from the edge of the nearest lane on which vehicles were travelling. For this investigation, the focus is to compare performance of different asphalt types, so the SPL produced as a single vehicle passed the microphone was measured and recorded. It was not necessary or relevant to undertake time-based statistical SPL measurements [e.g. Leq, L10(18hr), etc]. The SPL s of both northbound and southbound vehicles were recorded, the results averaged and compared between Test Point sites. Only single-vehicle-passes were measured (i.e. if there was both a northbound and a southbound vehicle passing the measurement point at the same time, or more than one vehicle passing-by in either direction, these measurements were ignored. Again, this was done to ensure valid comparative results between sites). 3 Measurements Measurements were undertaken at three locations, illustrated in the map below. Vehicle speed at these test points was found to be substantially the same so valid comparisons can be made between test-sites. Figure 2: Test Point Locations along Warrandyte Road

5 3.1 Test Point 1 Asphalt Texture: Smooth Asphalt Classification: Dense Graded Asphalt (see also Appendix) Average SPL*: 68.8 dba 3.2 Test Point 2 Asphalt Texture: Rough Asphalt Classification: Spray Sealed (see also Appendix) Average SPL*: 75.1 dba 3.3 Test Point 3 Asphalt Texture: Rough Asphalt Classification: Spray Sealed (see also Appendix) Average SPL*: 74.1 dba * SPL measured 6m from edge of road pavement

6 3.4 Comparative Summary The noise level produced by the asphalt at Sites 2 & 3 exceed the noise level at Site 1 by 5 to 6 db, as shown below. This demonstrates that significant noise reduction can be achieved by re-surfacing the road-pavement at Sites 2 & 3 with the same asphalt as used at Site 1. Test Point 1 Test Point 2 Test Point 3 Road Surface Macro-texture: Asphalt Classification (AS2702): Smooth Texture Dense Graded Rough Texture Spray Sealed Rough Texture Spray Sealed Noise level: 68.8 dba 75.1 dba 74.1 dba Noise level compared to Test Point dba dba Table1: Test Point 1 produced the lowest noise levels about 5 to 6dB quieter 3.5 Asphalt Textures At Each Test Site Figure 3: Left typical asphalt surface texture at Test Point 1 ( smooth quieter surface / dense-graded) Right typical surface texture at Test Points 2 & 3 ( rough noisy surface / spray-sealed)

7 3.5.2 Friction Coarse Asphalt / Open Graded Asphalt Test Points used along Warrandyte Road include two of the asphalt classifications as defined in Australian Standard AS2702 [Ref. 1]. A third type, classified as Friction Coarse / Open Graded, generates less noise that either of the types encountered on Warrandyte Road (see Appendix 5.2). Open-graded asphalt was initially used to improve the drainage characteristics of the pavement, through the introduction of voids into the structure of the asphalt. However it was subsequently found that this asphalt is much quieter than dense-graded types (i.e. that found at Test Point 1). Noise reduction from use of open-graded asphalt is generally in the range 3dB to 5dB when compared with dense-graded types [Ref. 4]. This level of reduction is maintained for at least 5 years. Use of open-graded asphalt on Warrandyte Road would reduce noise by 3 to 5dB at Test Point 1, and by 8 to 9dB when compared to Test Points 2 and 3. The total noise reduction that would be gained by use of open-graded asphalt is very significant indeed. 3.6 Equivalent Traffic Volume Referring to Appendix 5.1, a method is given for relating traffic volume (at peak times only) to changes in noise levels away from the road. Using this relationship and the difference in the noise produced by the different road pavement types found along Warrandyte Road, an equivalent traffic volume at peak times can be found. i.e. If the road pavement at Test Point 2 and Test Point 3 was changed to the same type as that at Test Point 1, then, the reduction is noise is at least 5dB (i.e. than change is -5dB), and: Equivalent traffic volume = 10 exp(-5/10) = 0.32 = 32% The above calculation makes the 5dB-reduction in noise very tangible, as it expresses the reduction in terms of traffic volume. It also underlines the significant returns gained though choice of appropriate road-pavement surface texture.

8 4 Conclusions The current use of rough-textured road-pavement (featuring exposed aggregate) along sections of Warrandyte Road is: magnifying noise from traffic by 5dBA to 6dBA when compared to the use of smooth textured (dense graded asphalt) surfaces along other sections of the same road. Re-surfacing Warrandyte Road from Tortice Drive to Falconer Road with the same asphalt (dense graded) as at Test Point 1 will reduce noise levels by 5 to 6dB is equivalent to reducing peak-hour traffic density to 32% of the existing level. Re-surfacing with an open-graded asphalt-type would result in: a further 3dB (at least) of noise reduction, resulting is a total reduction of 8 to 9 db The preferred course of action to reduce noise from Warrandyte Road is to: eliminate the use of rough-texture (e.g. spray-sealed) asphalt re-surface with open-graded asphalt type. Re-surfacing with a dense-graded type would also bring about significant benefits, but not to the same extent as for the open-graded type. Warrandyte Road will be subject to increased traffic volume when the Eastlink project opens in Re-surfacing Warrandyte Road with lower-noise asphalt will be highly beneficial in reducing noise immediately, and provide protection against additional noise from increased traffic volume in the future.

9 5 Appendix 5.1 Equivalent Traffic Volume At times of peak traffic flows, the distance between vehicles on the road is reduced, as shown below. This has the effect of increasing the overall noise level and making the noise nearly constant when plotted versus time (particularly when the distance from the road to the measurement location exceeds the inter-car-spacing). This effect is shown graphically below. Off Peak Times Peak Traffic Times Road & Cars Road & Cars Measurement Location Measurement Location dba dba Reduced noise level Same dba reduction in SPL by either: - quieter asphalt - or reduction in traffic to the equivalent traffic volume (see text) time time Figure 4: High traffic density at peak times results in noise levels away from the road becoming nearly constant. This is the basis for calculating the equivalent traffic volume. Noise reduction at peak traffic times can be achieved by either use of quieter asphalt or by a reduction in the traffic volume Because of the averaging effect at peak-times described above, the relation ship between the change in SPL (dba) and traffic volume is: Equivalent traffic volume ratio = 10 (change-in-spl)/10 NB: Change in SPL is a negative-number if the SPL is reduced.

10 5.2 Asphalt Classification to AS2702 Australia Standard AS2702 classifies asphalt surfaces into three main types: Asphaltic concrete (also referred to as dense graded asphalt) Spray Sealed (macro-texture features exposed aggregate on top) Friction Coarse (a smooth surface texture that also contain drainage voids) The photos below (from AS2702) show the macro-texture of these types. 6 References & Attachments 1. Australian Standard: Acoustics Methods for Measurement of Road Traffic Noise, AS ISO , Acoustics - Measurement of the influence of road surfaces on traffic noise - Part 1: Statistical Pass-By method 3. That s the Sound of Quiet Pavement - National Asphalt Pavement Association (USA) D:\miscellaneous\ road noise\thatsthes 4. Asphalt The Quiet Pavement, Asphalt Pavement Alliance, USA D:\miscellaneous\ road noise\asphaltth END

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