Although the freeway is open to traffic, various construction activities remain ongoing. These activities may include street improvements that require minor traffic shifts; landscaping; construction of the shared-use path; construction of the 32nd Street traffic interchange ramps; construction of the 59th Avenue frontage road in the I-10 Segment; rubberized asphalt paving; final striping and installation of reflectors on the east- and westbound lanes in the Pecos Segment; and other activities on I-10. The project is scheduled for completion in fall 2020.

Highway traffic as a noise source creates complexities when it comes to analysis and mitigation, and ADOT understands that you may have additional questions. There are many factors, all of which are relevant, such as traffic volumes and speed, traffic mix, pavement and atmospheric conditions that can impact noise levels. That is why the Federal Highway Administration has provided regulation and guidance on how to analyze and mitigate highway-related noise. The following resources provide information you might find useful:

ADOT will share the results of field noise measurements with its project partners, including members of the public and key stakeholders. ADOT will make every reasonable effort to address concerns and be innovative and flexible within the federal and state regulatory framework for noise mitigation. Keep in mind that if the noise levels (expressed in LeqA1h) are at or above 64 dBA, it does not guarantee a noise wall will be constructed, as other factors must also be considered. ADOT will explore other possible innovative methods to reduce noise levels.

Allow one to two weeks following testing for the team to analyze data and compile the technical memorandum. Once completed, ADOT will post information on the project website at SouthMountainFreeway.com. Schedules are subject to change because of the pandemic and other unforeseen situations.

Given the length of the corridor, number of residential areas and limited number of hours in the morning and afternoon for measurements, ADOT anticipates that each round of noise measurements will take approximately three to four weeks to complete. ADOT will make every effort to complete the measurements as quickly as possible, but also must account for unforeseen events that might require repeating of noise measurements.

At this time, ADOT is not scheduling noise measurements at specific homes or locations upon request. In alignment with the Final EIS, ADOT will conduct noise measurements in noise-sensitive areas along the entire corridor and share the results of decibel readings in correlation with each location.

While there are many factors that may have a potential to influence traffic noise, traffic volume is the predominant factor. With that said, traffic is at its loudest when the traffic operates at Level of Service C. This is the condition of a stable flow of vehicles, at or near free flow in a lane, but lane changing and maneuverability may be challenging. During Level of Service C at 70 mph, there are approximately 1,500 vehicles per hour and per lane. When traffic volumes increase beyond Level of Service C, vehicle speeds decrease and lower the noise levels.

ADOT utilizes data collected from the permanent automatic traffic recorders, an integral part of ADOT’s traffic data management system. That data will provide hourly/daily traffic patterns which, in turn, will provide the periods that the freeway operates at or close to “level of service c” – the highest level of traffic noise based on traffic volume and travel speeds. ADOT will continue to evaluate data and determine 2.5-hour windows of time - in the morning and afternoon - with similar traffic volumes when testing would occur.

Measurements will be taken at representative locations along the South Mountain Freeway; that is, residential neighborhoods, parks, schools and similar locations. Measurements are typically restricted to exterior areas of frequent human use. Interior measurements are taken only when there are no outside activities, such as at churches, hospitals and libraries.

Because of the COVID-19 pandemic, average daily traffic volumes throughout Maricopa county are lower than usual. Taking noise measurements during this pandemic is not representative of typical traffic noise levels. ADOT is planning to resume field noise testing in late summer/early fall 2020 and in late February/early March 2021. Beyond that, ADOT will continue testing noise levels throughout the 22-mile corridor regularly in select locations. Schedules are subject to change because of the pandemic and other unforeseen situations.