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ADOT I-17 Improvement Project

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Frequently Asked Questions


The I-17 Improvement Project extends along a 23-mile section of Interstate 17 between Anthem Way and Sunset Point.

The I-17 corridor is a vital tourism and commerce corridor, connecting the metro Phoenix area to northern Arizona. ADOT has identified I-17 as a Key Commerce Corridor, which prioritizes improvements to the transportation infrastructure while supporting the greatest potential commercial and economic benefits. Key Commerce Corridors connect the major economic centers of Arizona with local, regional, and international markets. These inter-regional routes are the most essential for future, quality economic development in Arizona and support high-quality job growth. Efficient movement of people, supplies, and goods support tourism, along with the growth and expansion of base industries and the state’s overall economy.

This project is divided into two segments and the improvements for each are detailed below.

Anthem Way to Black Canyon City (Widening) Improvements:

  • An additional northbound and southbound lane.
  • Northbound widening on the median side.
  • Southbound widening on the median side in some sections and widening on the outside in other sections.

Black Canyon City to Sunset Point (Flex Lanes) Improvements:

  • Construct two flexible travel (flex) lanes alongside the existing southbound lanes of I-17. The flex lanes will be separated from the southbound roadway by a concrete barrier.
  • Flex lanes will be open to northbound or southbound traffic, depending on the peak traffic direction and the greatest need.
  • Learn more on the flex lanes page.

All highways in Arizona are required to meet federal safety standards. The 23 miles of improvements, including the addition of one lane in each direction between Anthem Way and Black Canyon City and the flex lane improvements from Black Canyon City to Sunset Point, are expected to improve capacity and reduce congestion. The flex lanes will add capacity in the peak travel direction, as well as provide flexibility for managing traffic during maintenance activities, emergency situations and crash-related restrictions. Adding capacity improves safety by increasing the space between vehicles, providing drivers more time to make decisions. It's also up to all drivers to make good decisions behind the wheel, so crashes don't occur and cause unnecessary back-ups that affect everyone.

In the event of a crash that blocks lanes, both the flex lanes and the additional general purpose lanes will add capacity for drivers to travel safely through the affected areas.

Frontage road improvements are not included in this project.

Due to the very mountainous terrain, adding an additional lane on the northbound side of the highway would be very difficult – and costly. In addition, adding lanes to this segment would require severe restrictions during construction, with no viable detours, causing potential delays of two or more hours for drivers traveling through the work zone.

In order to extend the project all the way to Flagstaff, an extensive environmental study would need to be completed. This would require a significant amount of additional funding for the study, the design process, and the construction. Currently, no additional funding is available.

Widening the highway in both directions of the 23-mile section of I-17 was studied, however several factors contributed to the decision to deem it an unfeasible alternative during the environmental study.

Widening between Black Canyon City and Sunset Point:

  • Much of the northbound stretch of I-17 from Black Canyon City to Sunset Point is in an extremely mountainous area. This difficult terrain would require extensive modifications to the existing roadway to meet current design standards, beyond simply just widening the lanes and adding additional shoulder area.
  • Causing minimal disruptions to this highly traveled corridor was another major factor when considering alternatives. Widening the existing roadway would cause an extreme disruption to traffic over a prolonged period of time with no viable alternative route available.
  • To widen the lanes, complete closures of at least one and possibly both lanes in both directions would be needed to complete earthwork operations, including blasting and mitigation of rock fall hazards.
  • These factors would cause extreme traffic interruptions and the cost would be prohibitive.

Widening between Sunset Point and Flagstaff:

  • The environmental and preliminary design study was conducted between Anthem and Sunset Point. Several alternatives were considered and evaluated, and the widening and flex lanes alternative was selected as the preferred improvements.
  • Additional environmental studies would need to be conducted in compliance with the National Environmental Policy Act (NEPA). Those studies would identify the purpose and need for improvements; identify environmental effects of the project; and identify ways to avoid, minimize or mitigate impacts to the natural and human environment. If a preferred alternative was selected, additional funding would be necessary for design and construction.
  • There are currently no plans or funding for widening improvements from Sunset Point to Flagstaff.

This project was procured as a design-build-operate-maintain (DBOM), Public-Private Partnership (P3). This means that the developer team includes design, construction, operation and maintenance components to meet this contract. Since this is a DBOM project, design and construction may occur concurrently during some phases. In addition, the developer will operate the flex lane system for six months and maintain the flex lanes segment for three years following construction completion.

Traffic on weekends and holidays causes increased congestion, often creating long delays for drivers. This project will increase vehicle capacity and traffic flow, with the potential to alleviate certain traffic concerns and help create a safer corridor.

Interstate 17 is a heavily traveled corridor. The section that is being improved sees more than 1 million travelers annually. Traffic on weekends and holidays causes increased congestion, often creating long delays for drivers. This project will increase capacity in both the northbound and southbound directions, helping to alleviate traffic congestion. In addition, the creation of the flex lanes will allow peak traffic to flow faster and more efficiently. The increased capacity and improved traffic flow will help to improve safety for everyone on the road.

  • Flex lanes are a system that allows ADOT to vary the number of northbound or southbound lanes during peak travel times, or if there is a crash or another emergency situation that causes traffic delays.
  • Two additional lanes will be constructed adjacent to the existing southbound lanes. They will be open to northbound or southbound traffic, depending on peak travel times or the greatest need.
  • Overhead signage and electronic gates will alert motorists to which direction is open for traffic. The technology will be monitored and controlled by ADOT’s Traffic Operations Center.
  • Learn more on the flex lanes page.

No, these will be the first flex lanes on the state highway system.

  • I-5 Express Lanes (Seattle, WA)
  • I-90 (Seattle, WA)
  • I-25 Central Express Lanes (Denver, CO)
  • I-394 (Minneapolis, MN)
  • Reversible Express Lanes (Tampa, FL)
  • State Route 75 San Diego-Coronado Bridge (San Diego, CA)
  • I-35E and US 67 (Dallas, TX)

No, they will not.

Construction began in September 2022. ADOT anticipates work will last approximately three years.

The total current project cost is approximately $522,000,000, which includes the construction cost by the Kiewit-Fann Joint Venture developer team, along with ADOT’s cost to administer the project.

Project funding sources include:

  • $175.9 million from federal aid with matching state highway funds
  • $130 million of state highway funds appropriated by the state legislature in 2019
  • $90 million from an Infrastructure for Rebuilding America grant
  • $50 million programmed by the Maricopa Association of Governments for the Maricopa County portion of the project
  • $76,150,000 appropriated by the state legislature in 2023

Noise walls, the most common type of noise-reducing barrier, will be used in certain areas along the project corridor.

Noise walls are designed to limit traffic noise that travels into nearby areas. ADOT provides mitigation for traffic noise in accordance with federal requirements (23 Code of Federal Regulations CFR 772). A noise analysis is prepared for all projects that involve the following: construction of a highway on new roadway alignment; making a substantial change in the alignment of an existing highway; and adding new travel lanes to an existing highway.

ADOT conducted a noise analysis and determined that a noise wall barrier would be warranted in three sections of the project limits near Anthem, New River and Black Canyon City. Additional information about ADOT’s Noise Abatement Policy can be found on the website at:

Looking to stay involved in the project? Sign up for updates through our email blasts and traffic alerts, submit questions or comments through the project website, follow us on ADOT’s social media platforms, or keep up with construction by watching our progress live.

Stay up to date on this project by visiting the project website (, signing up for our emails, or following us on social media.

Kiewit-Fann Joint Venture is the developer team for the I-17 Improvement Project. Key members of the developer team include Kiewit Infrastructure West Co., Fann Contracting Inc., Kiewit Engineering Group Inc., DBI Services LLC, CONSOR Engineers LLC dba Apex Design, T.Y. Lin International, Lee Engineering, Terracon Consultants Inc., Wheat Design Group, Inc., Y2K Engineering, and Pinyon Environmental Inc.


We want you and our crews to get home safely. The speed limit along the entire 23-mile construction zone is 65 MPH. The speed limit is reduced to 55 MPH at night for lane closures and restrictions.

Construction began in September 2022. ADOT anticipates work will last approximately three years to complete. This timeline allows construction crews to minimize impacts on the traveling public while work is underway. The construction work will be done primarily during weekdays, with lane closures scheduled at night. There will be no scheduled weekend lane closures, allowing for access to I-17 during peak travel days and times.

The project website ( is a great resource for up-to-date information on this major project! Information is posted regularly under the construction tab, or you can sign up for construction updates/traffic alerts, visit or call 511 (except while driving).

Construction adjacent to the existing I-17 travel lanes will occur primarily during weekdays. Work that requires lane closures will be scheduled during weeknights. There will be no scheduled lane closures on weekdays, weekends or holidays, so I-17 traffic is not impacted by construction during peak travel days and times.

Throughout the 23-mile project, crews will replace two bridges and widen 10 others. Design and construction of the bridges will happen concurrently. For example, once a bridge design has been approved for construction, the design team will begin finalizing design of the next bridge. Once all designs are complete, drivers should anticipate seeing multiple bridges under construction at one time.

Construction is not anticipated to impact weekend or holiday travel. The construction work will be done primarily during the weekdays, with lane closures scheduled on weeknights, Sunday through Thursday on the northbound side and Monday through Friday on the southbound side. There will be no scheduled weekend lane closures, allowing for access to this corridor during peak travel days and times. Unscheduled restrictions or closures might be necessary in case of an emergency or other unplanned incident.


  • There will be no scheduled weekday or weekend lane closures.


  • The project will require lane closures, but the majority of them will occur on weeknights during the overnight hours. In the northbound direction, closures can occur between 6 p.m. and 6 a.m. beginning Sunday night and ending Friday morning. In the southbound direction, closures can occur between 7 p.m. and 7 a.m. beginning Monday night and ending Saturday morning.

Yes. Controlled rock blasting began in December 2022 and required full closures of I-17 in both directions to keep everyone safe, including the traveling public. The team conducted a total of 62 blasts at seven different locations along the project corridor over the course of a year. Approximately 177,000 cubic yards of rock and material was removed during the blasting process, then hauled to another area of the project to be reincorporated into the new roadway. A large portion of the blasted material is crushed and then used as aggregate base, embankment and rock mulch along the 23 miles of new lanes

Controlled Rock Blasting FAQs

All rock removed during the controlled rock blasting goes back into the project. The rocks are transported to one of two crushing sites, then crushed to the needed size and transferred to an area on the job where fill is required to build the new lanes. Much of the rock material from controlled rock blasting is being used as aggregate base in the paving of the new lanes.

Yes, intersections and freeway ramps will be closed during specific construction activities.

Yes, access to businesses will be maintained throughout construction. However, at times it might take longer to get to businesses along I-17 because of construction work.

Drivers can consult if they wish to take an alternate route. Closures for controlled rock blasting are typically scheduled Mondays through Thursdays from 10 to 11 p.m.

Flex Lane Operations

The speed limit will be 65 mph.

Dynamic overhead guide signs will alert drivers which direction is in use, and an electronic gate system will control access to the flex lanes. ADOT’s Traffic Operation Center will monitor and control the electronic gate system.

Should an incident occur within the flex lanes, traffic can be diverted back to the southbound lanes. Steel gates will be installed in the concrete barrier at four locations throughout the eight miles of flex lanes to allow emergency responders to clear traffic out of the flex lanes and into the general purpose lanes in the event of an incident. The gates are approximately 30 feet long and can be opened in either direction.

Yes, the flex lanes will have a shoulder to pull over, in case of emergencies.

State laws prohibit ADOT from restricting commercial trucks from using the flex lanes. However, signage will recommend slower-moving vehicles remain on the general purpose lanes.

No, however, signage will recommend slower-moving vehicles to stay on the general purpose lanes of I-17.

Yes, the flex lanes will include two lanes. Drivers can use the left lane to pass, if needed.

A specialized, automated net barrier and swing gate system at both ends of the flex lanes will be used to prevent vehicles from entering the flex lanes when traffic is flowing in the opposite direction. The ADOT Traffic Operations Center will control the gates and net barriers remotely and will monitor the flex lanes with cameras placed throughout the eight-mile flex lane corridor. In addition, dynamic overhead guide signs will alert drivers whether the flex lanes are open or closed in the direction they are traveling. Click here to watch a simulation of how the flex lanes will work.

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