The timeline represents the required steps in the development of a roadway or roadway improvement. In addition to establishing a funding source, there are 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.
The planning stage establishes the general location (alignment) and basic characteristics (number of lanes, type of traffic interchange, etc.) of a roadway. Accompanying this are environmental studies (noise, traffic volume, 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 phases of detailed engineering and technical review and interim levels of approval. 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. ADOT continually looks for ways to improve the construction process for maximum efficiency and minimal community impact. Once built, a roadway may be improved over time as a result of future studies.