(1) A regional transportation investment district planning committee shall adopt a regional transportation investment plan providing for the development, construction, and financing of transportation projects. The planning committee may consider the following factors in formulating its plan:

   (a) Land use planning criteria;

   (b) The input of cities located within a participating county; and

   (c) The input of regional transportation planning organizations of which a participating county is a member. A regional transportation planning organization in which a participating county is located shall review its adopted regional transportation plan and submit, for the planning committee's consideration, its list of transportation improvement priorities.

   (2) The planning committee may coordinate its activities with the department, which shall provide services, data, and personnel to assist in this planning as desired by the planning committee. In addition, the planning committee may coordinate its activities with affected cities, towns, and other local governments, including any regional transit authority existing within the participating counties' boundaries, that engage in transportation planning.

   (3) The planning committee shall:

   (a) Conduct public meetings that are needed to assure active public participation in the development of the plan;

   (b) Adopt a plan proposing the:

   (i) Creation of a regional transportation investment district, including district boundaries; and

   (ii) Construction of transportation projects to improve mobility within each county and within the region. Operations, maintenance, and preservation of facilities or systems may not be part of the plan, except for the limited purposes provided under RCW 36.120.020(8); and

   (c) Recommend sources of revenue authorized by RCW 36.120.050 and a financing plan to fund selected transportation projects. The overall plan of the district must leverage the district's financial contributions so that the federal, state, local, and other revenue sources continue to fund major congestion relief and transportation capacity improvement projects in each county and the district. A combination of local, state, and federal revenues may be necessary to pay for transportation projects, and the planning committee shall consider all of these revenue sources in developing a plan.

   (4) The plan must use tax revenues and related debt for projects that generally benefit a participating county in proportion to the general level of tax revenues generated within that participating county. This equity principle applies to all modifications to the plan, appropriation of contingency funds not identified within the project estimate, and future phases of the plan. Per agreement with a regional transit authority serving the counties participating in a district, the equity principle identified under this subsection may include using the combined district and regional transit authority revenues generated within a participating county to determine the distribution that proportionally benefits the county. Modifications made under section 5 of this act are in compliance with this equity principle. For purposes of the transportation subarea equity principle established under this subsection, a district may use the five subareas within a regional transit authority's boundaries as identified in an authority's system plan adopted in May 1996. During implementation of the plan, the board shall retain the flexibility to manage distribution of revenues, debt, and project schedules so that the district may effectively implement the plan. Nothing in this section should be interpreted to prevent the district from pledging district-wide tax revenues for payment of any contract or debt entered into under RCW 36.120.130.

   (5) Before adopting the plan, the planning committee, with assistance from the department, shall work with the lead agency to develop accurate cost forecasts for transportation projects. This project costing methodology must be integrated with revenue forecasts in developing the plan and must at a minimum include estimated project costs in constant dollars as well as year of expenditure dollars, the range of project costs reflected by the level of project design, project contingencies, identification of mitigation costs, the range of revenue forecasts, and project and plan cash flow and bond analysis. The plan submitted to the voters must provide cost estimates for each project, including reasonable contingency costs. Plans submitted to the voters must provide that the maximum amount possible of the funds raised will be used to fund projects in the plan, including environmental improvements and mitigation, and that administrative costs be minimized. If actual revenue exceeds actual plan costs, the excess revenues must be used to retire any outstanding debt associated with the plan.

   (6) If a county opts not to adopt the plan or participate in the regional transportation investment district, but two or more contiguous counties do choose to continue to participate, then the planning committee may, within ninety days, redefine the regional transportation investment plan and the ballot measure to be submitted to the people to reflect elimination of the county, and submit the redefined plan to the legislative authorities of the remaining counties for their decision as to whether to continue to adopt the redefined plan and participate. This action must be completed within sixty days after receipt of the redefined plan.

   (7) Once adopted by the planning committee, the plan must be forwarded to the participating county legislative authorities to initiate the election process under RCW 36.120.070. The planning committee shall at the same time provide notice to each city and town within the district, the governor, the chairs of the transportation committees of the legislature, the secretary of transportation, and each legislator whose legislative district is partially or wholly within the boundaries of the district.

   (8) If the ballot measure is not approved, the planning committee may redefine the selected transportation projects, financing plan, and the ballot measure. The county legislative authorities may approve the new plan and ballot measure, and may then submit the revised proposition to the voters at the next election or a special election. If no ballot measure is approved by the voters by the third vote, the planning committee is dissolved.