Spine Corridor Study I-10 I-17

Study Overview

MAG along with the Federal Highway Administration (FHWA) and the Arizona Department of Transportation (ADOT), launched a study to develop a Corridor Master Plan for the I-10 and I-17 corridor. The project’s planning efforts began in April 2014 and concluded with MAG Regional Council acceptance of the project’s Recommended Alternative on May 24, 2017 into the MAG 2040 Regional Transportation Plan. On March 28, 2018, representatives from the Arizona Department of Transportation, Federal Highway Administration – Arizona Division, and the Maricopa Association of Governments, signed a Planning and Environmental Linkages (PEL) Statement summarizing the findings of the project.

I-10 I-17 Corridor Map
Click to view The larger version of this image.

The study area was the 31-mile corridor beginning at the I-17/Loop 101 (North Stack) interchange , through the I-10/I-17 (The Split) interchange, and down the 10 to the interchange with Loop 202 (Pecos Stack). This corridor is referred to as the “Spine” because it serves as the backbone for transportation in the metropolitan Phoenix area. The corridor handles more than 40 percent of all daily freeway traffic in the region.

The Spine Study analyzed long-term strategies to improve mobility in the corridor. The study evaluated the full range of transportation modes and concepts to identify the best multimodal solutions. These long-term solutions are viewed as a combination of traditional methods, new technology, and increased use of transit. The key outcome of the Spine Study is a detailed strategy to manage traffic in the I-10 and I-17 corridors through 2040. Recommendations are programmed in the MAG Regional Transportation Plan and Transportation Improvement Program.

The following document has been prepared summarizing the study process, purpose and need, public outreach, the recommended alternative, and the initial environmental findings that have been documented.


Key Components of Final Recommendations

  • Improve safety by bringing interstates up to current design standards
  • Create continuous managed lane system by adding new managed lanes (such as HOV lanes)
  • Add a minimum of one lane throughout entire corridor (HOV, general purpose, or collector distributer)
  • Modernize 24 of the 31 traffic interchanges in the corridor, including adding 5 new direct HOV ramps and new interchanges
  • Promote pedestrian and cyclist connectivity throughout the corridor by creating safer pedestrian and bicycle crossings at 20 locations, including 9 separate structures
  • Coordinated crossings of light rail transit at four locations
  • Exact changes and their locations can be seen on our interactive map: interactive map of the Corridor Master Plan Recommendations

Study Process

The Spine Study analyzed long-term strategies to improve mobility in the corridor. The study evaluated the full range of transportation modes and concepts to identify the best multimodal solutions. The study sought to incorporate a combination of traditional methods, new technology, and increased use of transit in order to manage traffic along these corridors through 2040.

Related Documents
Spine Study Public Meeting
Public open house participants in Guadalupe, AZ

Public Engagement

In the spring of 2015, the MAG, in partnership with the FHWA and ADOT, held the first round of public meetings to share information about the Spine Study and obtain public comment on potential corridor improvements. Members of the public were encouraged to attend the meetings or participate by completing an online survey. Nearly 1,800 members of the community provided their comments during this process. The spring 2015 Agency and Public Involvement Summary Report is included as Appendix J of the Interstate 10/Interstate 17 Corridor Master Plan (FY 2014) Needs Assessment Report.

The initial input in 2015 helped MAG create recommendations for improvements along this corridor. These recommendations were brought to the community for feedback in 2017. In addition to great meeting attendance at our public open houses in January 2017, we had hundreds of people complete our online survey. After reviewing all the feedback received, the study team suggested the following revisions to the I-10/I-17 Corridor Master Plan Recommendations:

  • Bicycle/Pedestrian Bridge over I-17 at Osborn Road or Grand Canal: Based on considerable feedback during the comment period against this improvement, the recommendation to construct a bicycle and pedestrian bridge over the freeway as outlined in Phoenix's 2014 Comprehensive Bicycle Master Plan was removed.
  • I-10 and Sky Harbor Circle North Direct High Occupancy Vehicle (DHOV) Ramps: Based on recent planning developments related to the western entrance to Phoenix Sky Harbor Airport, the idea to construct DHOV ramps within the median of I-10 to Sky Harbor Circle North was removed from the recommendations.
  • I-17 and Glendale Avenue Interchange Improvement: Based on feedback received during the comment period, the reconfiguration of I-17/Glendale Avenue into a high-capacity traffic interchange was added to the recommendations. This could better accommodate large east-west arterial movements on Glendale Avenue and improve bike and pedestrian safety.
  • Bicycle/Pedestrian Bridge over I-10 at Knox Road: Based on feedback received during the comment period, a bicycle/pedestrian bridge over I-10 was added at Knox Road to support the BIKEiT Seat Route bike boulevard as outlined in Tempe’s 2015 Transportation Master Plan.
Related Documents:

Evaluation Criteria

Ideas for corridor improvements were evaluated with the following criteria (in no particular order):

  • Consistency with public feedback
  • Engineering
  • Environmental
  • Operations
  • Safety

For more information on the evaluation criteria, check out Banner: How did we evaluate the options?

Reports, Presentations, and Studies

You can download the entire Alternatives Screening Technical Report here (218 pages, 67.7 MB), and download appendices A-E here (490 pages, 63.9 MB) and F-H here (402 pages, 69.2 MB.


Project Presentation

On March 29, 2018, the MAG and HDR Consultant project managers made a presentation on their lessons learned on conducting this effort at the 67th Arizona Conference on Roads and Streets in Tucson, Arizona. The following is a link to that presentation.

Previous Environmental Studies on I-10 and I-17

ADOT and FHWA were previously developing design concept reports and environmental impact statements as part of the I-10 Corridor Improvement Study and I-17 Corridor Improvement Study. These studies examined ways to add capacity, such as general purpose lanes, to both I-10 and I-17 in the Phoenix area.

The two previous studies identified long-term improvements that would have required more funding than was available in the Regional Transportation Plan. However, the studies also identified a number of near-term improvements that will be carried forward and implemented by ADOT through a separate but parallel effort.

ADOT and MAG agreed, and FHWA accepted, the decision to rescind the studies in 2012 after it was determined that separate studies may not result in the best overall plan and that many of the studies' recommendations were not prudent. It is important to note that many of the planning, engineering and environmental information from those studies were folded into the new Corridor Master Plan.

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About MAG

The Maricopa Association of Governments (MAG) is a Council of Governments (COG) that serves as the regional planning agency for the metropolitan Phoenix area.

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