Factors considered in the environmental study were the amount of truck traffic that would use the freeway and its potential impact on the surrounding community. The MAG regional travel demand model forecasts approximately 10 percent truck traffic on the South Mountain Freeway in 2035. The forecasted truck traffic is based on existing traffic studies and projected socioeconomic data. This percentage is similar to current traffic conditions on I-10 between Loop 101 and I-17 and on US 60.

Chapter 3 of the Final Environmental Impact Statement (FEIS) states traffic projections estimate approximately 117,000 to 190,000 vehicles daily would use the South Mountain Freeway in 2035.

Air quality impacts were estimated through sophisticated computer modeling based on predictions of the amount and nature of traffic under worst-case scenarios. The emissions models are based on extensive emissions testing that the U.S. Environmental Protection Agency (EPA) has conducted on thousands of vehicles representative of the ages and models of the vehicle fleet on the roads today.

While efforts to study alternatives on Community land were attempted, the Community has long held a position of not allowing the freeway to be located on its land. For example, a coordinated referendum of Community members to favor or oppose construction of the freeway on Community land or to support a no-build option occurred in February 2012, and Community members voted in favor of the no‑build option. Therefore, the freeway cannot be located on Community land.

The study did consider a variety of transportation alternatives, modes, and strategies that would fit into the Regional Transportation Plan, including transit. The freeway option was determined to best meet the purpose and need for the project, following an extensive screening process which included evaluation of additional benefits such as system linkage, regional mobility, and consistency with regional and local long-range plans.

Public input was a vital component during the environmental study phase and was solicited from project inception through key milestones in the Draft and Final Environmental Impact Statement (EIS) processes. The interests and needs of the public, along with all other social, economic and environmental issues and impacts, were fully analyzed during the study phase of the project.

The route for the freeway was determined through a multidisciplinary process to identify a range of reasonable alternatives that were studied in detail in the Environmental Impact Statement. The study process involved identifying, comparatively screening, and eliminating alternatives based on:

The SMF has been a critical part of the MAG Regional Freeway Program since it was first included in funding approved by Maricopa County voters in 1985. The SMF was also part of the Regional Transportation Plan funding passed by Maricopa County voters in 2004 through Proposition 400. The SMF is a key component of the region’s adopted multimodal transportation plan and the Regional Freeway and Highway System and is the last piece to complete the Loop 202.

The 40th Street, Estrella Drive and Vee Quiva Way interchanges provide the Gila River Indian Community direct access to and from the freeway. The Gila River Indian Community is responsible for connecting to the traffic interchanges, in coordination with appropriate jurisdictions.

The South Mountain Freeway will be constructed as an eight-lane freeway (three general purpose lanes and one HOV lane in each direction). There are no current plans to widen the freeway in the future.