Wisconsin Department of Transportation

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I-94 (US 12-WIS 65) Corridor Study - Frequently asked questions (FAQ), Traffic noise

FAQ - Basics | FAQ - Aug. 2013 | FAQ - Noise

Will WisDOT consider noise levels as part of the I-94 expansion study?

Yes, it is part of a federal requirement. U.S. noise regulation (23 CFR 772) requires state highway agencies to determine noise impacts and evaluate possible mitigation measures as part of a proposed Type I Federal Aid project. I-94 is considered a Type I project since it would add through traffic lanes.

How does WisDOT determine where to place noise barriers?

The Traffic Noise Model (TNM 2.5) is used to predict future traffic sound levels. Impacted locations are then considered for noise abatement measures. Project staff evaluates potential design and traffic control modifications, such as prohibiting trucks or changing the horizontal or vertical alignment. Then, noise barriers are modeled for attenuating noise and are optimized to ensure a beneficial and economical barrier is designed. After the evaluation, a determination is made whether each barrier is a feasible and reasonable mitigation measure.

What is an impacted receptor?

An impacted receptor/listener or common use area is one with:
A predicted future traffic sound level which approaches or exceeds the WisDOT Noise Level Criteria (NLC) for Considering Barriers for different land use categories; or when predicted future traffic sound levels exceed existing levels by 15 decibels (dB) or more.

NLC is divided into land use categories that include residential areas, serene/quiet lands, parks, schools, hotels, offices, etc.

Would there be impacted receptors along I-94 if the roadway is expanded?

Yes. Approximately 80 receptors were modeled as part of the noise analysis for the study project. Approximately 15 receptors would be considered impacted since future noise levels are anticipated to approach or exceed the NLC.

What does feasible and reasonable mean?

Feasible and reasonable is set by Wis. Admin Code Trans 405. For a noise abatement measure to be feasible, a minimum of one impacted receptor or common use area must achieve a five dB noise reduction. For a noise barrier to be reasonable, the total cost may not exceed $30,000 per benefited receptor. To be considered a benefit, an impacted receptor must receive a minimum of eight dB noise reduction.

Typically, how effective are noise barriers?

Effectiveness depends on the distance between the impacted receptor and the barrier. For areas located directly behind a barrier providing an eight dB reduction, the noise level will be perceived as being cut in half. This benefit decreases as a listener moves farther away from the barrier and is negligible at distances greater than 300 feet.

Graph depiciting noise barrier effect vs. distance from construction site.

Are noise barriers reasonable for the I-94 Expansion Study?

Noise barriers were evaluated in the areas of the impacted receptors. The noise barriers would be well in excess (three to 16 times) of the reasonable cost of $30,000 per benefited receptor. In some instances a wall cannot be constructed high enough to provide noise reduction benefit due to the rolling topography and distance of the receptor from the highway. Most of the 15 impacted receptors are located 300 to 500 feet from the roadway where barriers are ineffective at reducing noise levels.

Will WisDOT consider noise levels during construction?

Yes. The noise generated by construction equipment will vary greatly, depending on equipment type/model/make, duration of operation and specific type of work effort. Typical construction noise levels are shown in the table below.

Distance from construction site (feet)/Range of typical noise levels (dBA)

100/69 - 89
200/63 - 83
300/59 - 79
400/57 - 77
500/55 - 75
1,000/49 - 69

WisDOT considers compliance with local noise ordinances governing the hours for operation of construction equipment when planning for a project. Additional investigation and coordination is required by the project team to determine what operations will occur during nighttime hours. Measures to limit noise generating activities, such as pile driving and pavement breaking, will be considered where feasible. Since maintenance of safety and mobility are a high priority on I-94, nighttime work is anticipated during construction to allow for off-peak lane closures.

Can WisDOT post engine braking restrictions at the truck weigh enforcement facility?

No. Engine braking is often a function of safely slowing or stopping an entering truck at the weigh facility. Typically WisDOT may permit local governments to place signs on highways under WisDOT jurisdiction if that local unit of government has a community wide noise ordinance that they actively enforce. The engine braking signing may be installed only on conventional highways at or near the corporate limits of the community.

Engine braking signing cannot be used at site specific locations on conventional roadways, freeways, expressways, or interchange ramps per WisDOT policy.

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WisDOT Northwest Region Office, nwr.dtsd@dot.wi.gov
Last modified: August 26, 2013

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