The timeline represents the required steps in the development of a roadway or roadway improvement. In addition to establishing a funding source, there is a series of required planning and environmental studies before a roadway is constructed.


In November 2004, Maricopa County voters approved a 20-year extension of a half-cent sales tax until December 31, 2025, to fund a comprehensive package of transportation improvements as part of a Regional Transportation Plan. Funding for the plan, which includes $9 billion in regional freeway improvements in Maricopa County, became effective January 1, 2006.

Responding to federal transportation planning requirements, the RTP is being extended through 2031 by the Maricopa Association of Governments (MAG) to maintain a 20-year planning horizon. As a result, a fifth phase has been added to the RTP, covering the period from 2026 through 2031. Consistent with federal planning guidelines, funding for transportation projects is based on revenue sources that are considered to be reasonably available for the planning period. This assumes that for planning purposes funding sources with a long history of providing funding in the past will continue into the future. 

In fall 2009, due to declining sales tax revenues and decreases in other transportation revenue sources to fund improvements, MAG recommended that some future projects be deferred to Phase V of the plan. As part of the planning process, project costs and funding levels are continuously monitored, and the RTP is periodically updated to take advantage of cost savings or changes in the transportation revenue outlook. This can result in the acceleration of projects that were formerly deferred. For more information about RTP projects deferred to Phase V in the MAG tentative scenario, please visit the MAG Web site.

Freeway planning to determine potential future corridors and freeway improvements is conducted well in advance of design and construction. Area population growth, future land use, jurisdictional responsibilities, and other factors are used to determine the need, feasibility and general location of future freeway improvements.


The study stage establishes the location (alignment) and basic characteristics (number of lanes, type of traffic interchange, etc.) of a roadway. Accompanying this are environmental studies (noise, economic impacts, etc.), identification and evaluation of alternatives, general cost estimates, coordination with public and private partners and the determination of feasibility to move to the design phase.


The design of a roadway involves several stages of detailed engineering and technical review and interim levels of approval. Project information is shared and discussed with the public at project milestones, and public input is considered in the evaluation of alternatives. The final design of the roadway is represented in plans and specifications that construction contractors use to prepare construction bids.


Road construction for projects is based on detailed plans and specifications provided to the contractor following the approved design. As the construction process advances, changes may occur that are influenced by a variety of factors. ADOT continually looks for ways to improve the construction process for maximum efficiency and minimal community impact. Once built, a roadway will be maintained and improved over time as a result of future growth and transportation needs.


ADOT continually plans for enhancements to the roadway once it is built and in use for maximum efficiency and safety. Various studies identify these enhancements and may influence additional planning, design and construction. Studies for the Loop 202 (Santan Freeway) are on the Current Studies page.

Our Valley Freeway System is part of the 2004 voter-approved Regional Transportation Plan. We are working hard with our transit partners to implement the voters’ vision and are committed to quality, safety, open communication with our neighbors, and minimal inconvenience to the traveling public.