About The DOT

Highway funding in Iowa

Note: Information on this webpage was last updated in March 2020

State highways maintained by the Iowa Department of Transportation (Iowa DOT) are financed with funds that are principally derived from vehicle fuel taxes and registration fees collected and allocated by the state and federal governments.

State funding/allocation

Road Use Tax Fund (RUTF): Dedicated highway user revenue, collected through a state excise tax on fuels, is deposited into the Iowa Road Use Tax Fund (RUTF). No State of Iowa general fund (i.e. general tax) revenue is used for highway projects in Iowa. Established in 1949 by the 53rd Iowa General Assembly, the RUTF has provided a stable and reliable source for investing in the state’s primary, secondary and municipal roadway systems. After some off-the-top diversions, receipts into the RUTF are distributed according to a formula of 47.5 percent for the primary road system, 24.5 percent for secondary county roads, 8 percent for farm-to-market county roads, and 20 percent for city streets. Legislation that went into effect in 2003, which involved the transfer of jurisdiction of some roadways from the state to either a city or county government, requires a share (1.75 percent) of the primary road system funds be paid to local governments.

State Excise Tax on fuels – (cents per gallon)1

Iowa motor fuel tax1 Tax
Gasoline, including ethenol blends E110 and E-14 30
Ethanol-blended gasoline2 (Fuel that has been blended with alcohol distilled from cereal grants, the end product containing at least 15 percent alcohol) 24.5
Aviation gasoline 8.0

Diesel, including biodiesel B10 or lower 32.5
Diesel B11³
Aviation jet fuel
Liquefied petroleum gas (LPG)
Compressed natural gas (CNG)
Liquid Natural gas (LNG) 32.5

Other Cubic Feet
Biofuel (Defined as any oxygenated product derived from soybean oil, vegetable oil or animal fats that can be used in diesel engines or aircraft. Biofuel may be a blend of diesel fuel or it may be 100 percent soybean oil, vegetable oil or animal fats. Any biofuel product is taxed as special fuel.) Per gallon rate is the same as the Motor Fuel Tax

1Rates as of July 1, 2023. Excise taxes are governed by Iowa Code 452A.3. Only dyed diesel fuel used for off-highway purposes and fuel exported outside of Iowa is sold tax-free.

2On July 1, 2023, the rates for ethanol-blended gasoline E-15 or higher changed – from 20.4 cents per gallon and 24.5 cents per gallon.

TIME-21: In 2008, an additional stream of state revenue was established through legislation creating a separate “TIME-21” Fund. This revenue is dedicated to maintenance and construction of certain primary highways in the state (60 percent), secondary roads (20 percent) and municipal streets (20 percent).

On July 1, 2023 the rate for diesel B11 or higher changed from 30.1 cents per gallon to 29.8 cents per gallon.

TIME-21 was a response to a “perfect storm” of factors threatening to create an estimated $267 million per year funding shortfall, hindering the state’s ability to adequately maintain and improve public roadways in Iowa. Those factors include a large and aging public roadway system, increasing demands on that system, flattening revenue, and increased construction costs.

The new revenue stream, which helps to address the projected shortfall, was created by changing certain vehicle registration fees and schedules, and by increasing trailer registration and title fees.

Total state funding

For state FY 2020, receipts into the RUTF and the TIME-21 fund are estimated to be $1.723 billion, comprised of $663 million in fuel taxes, $972 million in various registration fees, plus $88 million from miscellaneous other sources.

Primary Road Fund: Of the $1.883 billion in total state funding estimated for FY 2024, approximately $916 million is deposited into the Primary Road Fund. The Primary Road Fund is the major source of funding appropriated by the legislature on an annual basis for the Iowa DOT’s operations budget (there is also a smaller amount appropriated annually by the legislature from the Road Use Tax Fund for Iowa DOT operations to cover activities that go beyond support of just the primary road system). For FY 2024, approximately $356 million was appropriated from the Primary Road Fund for Iowa DOT operations budget.

The remaining balance of Primary Road Fund revenue (estimated to be $548 million in FY 2024) is then available for the Commission to program on road and bridge projects on the primary road system. In addition to the state funding from the Primary Road Fund, approximately $497 million of federal funding (described in the next section of the guidebook) is also available for the Commission to program on road and bridge projects on the primary road system.

Allocation of state funds: Iowa’s Five Year Transportation Improvement Program is developed yearly by the Iowa Transportation Commission with input from Iowa DOT staff and the public. It describes planned investments in Iowa’s multimodal transportation system, including aviation, transit, railroads, trails and highways. For FY 2024-2028, approximately $4.3 billion is forecast to be available for highway right of way and construction.

Current five-year program

Federal funding sources

Overview: In addition to state revenue, highway projects in Iowa are funded via federal programs. The primary funding source for these federal programs is revenue from federal taxes on motor fuel and other user fees which flow into the federal Highway Trust Fund (HTF). The HTF was created through enactment of the Highway Revenue Act of 1956. The taxes are collected by the federal government and placed in the HTF which consists of two accounts: the Highway Account, and the Mass Transit Account.

Current federal taxes on motor fuel and special fuel (cents per gallon)

  tax rate to highway account to transit account LUST fund
Gasoline/Gasohol 18.4 15.44 2.86 0.1
Diesel 24.4 21.44 2.86 0.1
Petroleum Gas 18.3 16.17 2.13  
Compressed natural gas 18.3 17.07 1.23  
Liquid Natural Gas 24.3 24.44 1.86  

Federal dollars back to Iowa

The federal funds are apportioned (returned) to the states per provisions in the Infrastructure Investment and Jobs Act which was passed by Congress on Nov. 15, 2021, and signed the following day (PL 117-58). The FAST Act reauthorized surface transportation programs through Sept. 30, 2026. Most federal transportation taxes, including those on gasoline and diesel fuel, are authorized through Sept. 30, 2026.

The total of apportionments and allocations paid out nationally now exceeds revenue contributed to the trust fund because federal general fund dollars have been added to the HTF in recent years to supplement the revenue. A combination of factors has made the revenue stream inadequate to fund the programs and projects the HTF was intended to cover. These factors include inflation, higher gas mileage and use of vehicles powered by electricity.


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