Noise Analysis Guidance on Peak Shoulder Lane Use

Noise is an inevitable part of everyday life in a today’s rapidly growing world. Traffic noise is one of the most common noise sources that has the potential to adversely affect communities. But how do we minimize traffic noise impacts while still trying to maximize capacity and efficiency? Many transportation departments across the country are experimenting with utilizing shoulder lanes during peak commute hours to reduce congestion. However, using shoulder lanes will move traffic closer to nearby sensitive receptors such as homes, schools and places of worship which may result in greater noise impacts on these sensitive receptors. Determining the extent of the noise impacts is required to evaluate noise abatement and further weigh the pros and cons of the project.    An example of the debate for using shoulder lanes is the Washington State Department of Transportation (WSDOT). WSDOT is considering repurposing shoulder lanes during peak congestion hours along Interstate 90 (I-90), approximately 10 miles east of Seattle between the cities of Bellevue and Issaquah. The proposed improvements would involve re-striping and shifting of current travel lanes to allow for an additional shoulder lane within the same roadway footprint. As shown in Figure 1, electronic signage would signify to drivers if a shoulder lane is open or closed for vehicular traffic and all vehicles, with the except of heavy trucks, would be permitted to use the shoulder lane.   As a part of the evaluation, a traffic noise study for the project was completed to assess future noise levels

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