AsphaltTheQuietPavem ent

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ASPHALT: THE QUIET PAVEMENT www.AsphaltAlliance.com

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Asphalt Pavements are Quiet

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“Pavement/tire noise has been studiedfor well over 30 years and several large databases have been compiled in the last decade. NCHRP Synthesis 268 is a summary of the research findings of this extensively studied topic.”

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FHWA - Noise Abatement Criteria 67 dB(A) “this is not an absolute value or design standard, only a level where noise mitigation must be considered”

The Decibel Scale: 

The Decibel Scale Hearing Threshold Conversation Pain Threshold Discomfort

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The Decibel Scale Increasing the decibel level by 10 doubles the noise intensity! Conversation Train Chain Saw

Noise Walls: 

Noise Walls Effective only for those in line-of-sight. Do not reduce noise at source.

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Effectiveness must justify expense. Cases: I-40, Knoxville: >$25,000/home I-285, Atlanta: Requirements of > 69 dB(A) and < $50,000/home U.S. 441, West Boca, FL: > 67dB(A), <$30,000/home, reduction of > 5dB(A) Nationwide (FHWA, 1998): >$1M/mile Noise Walls

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Conclusions, “In general, when dense-graded asphalt and PCC pavements are compared, the dense-graded is quieter by 2 to 3 dB(A)” Surface Texture

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67 dB(A) 50 ft The Decibel Scale

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A reduction of 3 dB(A) is like doubling the distance from the noise. 67 dB(A) 100 ft - 3 dB(A) = 64 dB(A)

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Conclusions: “In general, when dense-graded asphalt and PCC pavements are compared,the dense-graded is quieter by 2 to 3 dB(A)” A 3dB(A) reduction corresponds to: - doubling the distance - reducing traffic volume by 50% - reducing traffic speed by 25%

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Conclusions: “Open-graded asphalt shows the greatest potential for noise reduction for passby noise. Reduction when compared to dense-graded asphalt ranged from 1 to 9 dB(A).” A 9dB(A) reduction corresponds to: - a reduction in traffic noise by almost 50%!

OGFCsReduce Noise and Improve Visibility: 

OGFCs Reduce Noise and Improve Visibility

Noise ReductionOpen vs Dense Graded Mixes: 

Noise Reduction Open vs Dense Graded Mixes Source: NCHRP 284

What Can Be Done?: 

DOTs indicate a strong need for pavement noise control strategies. Proper selection of pavement surface is the best method to reduce noise from pavement/tire interactions. What Can Be Done?

Effect of Pavement Surface: 

OGFC is the quietest surface type. (Wayson, NCHRP Synthesis 268) SMA has also proven to be a quiet surface. (Wisconsin DOT, 1993) Dense graded HMA surfaces are quieter than PCC pavements.(Hibbs and Larson, Report FHWA-SA-96-068, May 1996) Effect of Pavement Surface

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Noise Makes News! Families Near I-275 is lobbying the Michigan DOT for sound abatement. In 1999, MDOT rebuilt I-275 with concrete. Residents contend the project has increase noise levels. Levels have been registered upwards of 90 decibels. Steve Phillips of Berkshire, England-based TRL Limited spoke about England’s 10-year plan to install quieter surfaces on 60% of main trunk roads. The surfaces will be SMA or OGFC.

Summary: 

Summary Highway noise is important to the public. Small changes in dB level are noticeable. Decrease of 9 dB(A) reduces noise by 50% Decrease of 3 dB(A) is like doubling distance

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Summary Noise walls can work, but: They are expensive. They don’t work in all types of terrain. Source of noise is still there. Asphalt pavements can reduce noise at the source by up to 9 dB(A).

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Hot Mix Asphalt Summary Asphalt pavements for noise reduction in order of effectiveness: OGFC SMA Dense-Graded HMA PCC