renaldo lorio adrian jongens gerrie van zyl emile du preez sat seminar feedback road noise study

MYCUBE ASSET MANAGEMENTSYSTEMS (PTY) LTDMYCUBE ASSET MANAGEMENTSYSTEMS (PTY) LTD

Renaldo LorioAdrian JongensGerrie van ZylEmile Du Preez

SAT Seminar Feedback

Road Noise Study

MYCUBE ASSET MANAGEMENTSYSTEMS (PTY) LTDMYCUBE ASSET MANAGEMENTSYSTEMS (PTY) LTDBackground

• National road network a generally high speed road network

• Many sections of the national road network traverse in close proximity to residential areas (noise sensitive areas)Development crept closer to the national roads

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Background

• More complaints are being received of late (Mossel Bay, Colchester amongst others)

• In the past road noise was dealt with intuitively (use of OGA and UTFC in close proximity to noise sensitive areas)

• Did not properly understand the properties of the materials w.r.t. noise

• Somewhat averse due to high L.C.C.• Initiated road noise study in 2012

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Scope

• Study Need Understand road noise RequirementsEffect of different surfacing typesMeasures to reduce noise levels on N2/6Recommend strategy

• Dissemination of informationSAT SeminarsSummary report after review


Sources of traffic related noise

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Summary

• Understanding road noisePropulsion noise ( Engine, gearbox etc.)Rolling Noise

• Radial vibrations

• Air pumping

• Slip-stick (High frequency effect of tyre on smooth floor)


Summary

• Rolling noise amplificationHorn effect

• Texture


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Noise mitigation

• Minimise at source (most effective)• Speed reduction (e.g.120km/h to 100km/h)

Not significant effect• Half the speed - 2dBA noise reduction

• Separation distanceDoubling the distance - reduce 3dBA

• Noise barriersExpensivePartially effective


Road noise measurements

• Measurement methods Close Proximity Method

• Cannot be used to calculate LAeq

Statistical Pass-by Method• 7.5 – 10m from lane• 1.4m high

• Results LAmax

Calculation • LAeq

Microphone

Microphone pre-amplifiers

Sum sound intensities at each frequency

A-weighted sound spectrum levels


Existing surfacings investigated

• Existing (old) surfacing types measured9,5 mm UTFC13,2 mm UTFC6,7 mm UTFC9,5 mm SMAContinuous graded asphaltCGA with rolled-in chips (13,2 mm)9,5 mm Single seal13,2 mm Single seal13,2 + 6,7 mm Double seal


Results

Note: Values represent only single surveys – Not a representative sample


Ideal

• Reduce road noise at source Reduce texture depth

• (Within safety limits)

Short & equal wave length (Aggregate size <8mm) Negative texture as far as possible

• Aggregate shape• Construction e.g. Rolling practices

Increase porosity/ interconnected voids and thickness Binder type (Bitumen rubber)

Positive textureNegative texture


Ideal

Microflex 0/6

Porosity 15% Thickness 2.5 cm

2.5cm

4.5cm

Twinlay 4/8 – 11/16

• Affordability ?


Seal trials to reduce noise N2-6

• Resealed with 19/9 double seal • Increase in road noise after reseal of N2/6• Complaints• Purpose of this experiment

Improve road noise through seal treatments Measure impact on road noise Measure texture depth and skid resistance


Treatments

Existing 19/9 – No loss (Reference) 19/9 + Grit 19/9 + 6.7mm

19/9 + Fine Slurry 19/9 Close packing 19/9/9 Split seal


N2/6 Results – Noise Improvement Trials

4.7 dBA


Conclusions

• Only one surfacing with LAeq less than 65 dBA

• Seals generally Higher LAeq than paved asphalt

• 9.5 UTFC not performing as expected• Speed does not make a big difference• More measurements required

To determine longer term effects and ranges• N2/6 trials

All trials showed improvementSlurry option LAeq = 4.7 dBA (significant reduction)


Strategy Forward

• Noise mitigationCombined responsibility

• Land use planning • Cost of noise barriers

Surfacing type selectionImprove rolling noise at source


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END

renaldo lorio adrian jongens gerrie van zyl emile du preez sat seminar feedback road noise study

Documents

noise levels

effective slide

past road noise

noise mitigation

review slide

double seal slide

smooth floor slide

representative sample