Establishes a 50% tax on road projects, funded by the state, and establishes the "State Road Project Fund"

HB 1600 requires the state to pay a 50% tax on the total cost of any state-funded road project (including materials, labor, and equipment) upon completion. The tax revenue is deposited into a new "State Road Project Fund," managed by the state treasurer. This dedicated fund must be used exclusively for planning, constructing, maintaining, and acquiring materials for interstate/primary highways, county bridges, and related infrastructure. Funds remaining at the end of a biennium cannot revert to general revenue, and interest earned on fund investments is added to the fund.