According to the September transportation revenue forecast, transportation revenues are expected to total $8.115 billion in 2023–25, $8.909 billion in 2025–27, and $10.853 billion in 2027–29. Over this three-biennia period, the revenue forecast is $144 million lower than forecasted in June. However, the September forecast is still $136 million higher than expected in the enacted transportation budget (which balanced through 2027–29).

Although the enacted budget included new revenues (and an automatic annual increase to the gas tax), inflation-adjusted transportation revenues are expected to decline each year beginning in 2029. The motor vehicle fuel tax makes up the largest share of total transportation revenues (38.6% in 2025), and it is a major contributor to the inflation-adjusted decline. Adjusted for inflation, from 2024 to 2035, motor fuel tax revenues are expected to decrease by 4.4% while total transportation revenues (excluding transfers) are expected to increase by 14.0%.

A major reason for the reduction to the forecast since June is that gas consumption is now expected to be significantly lower.

Some of the decline in inflation-adjusted gas tax revenues over time is counteracted by increases in electric vehicle fee collections. Revenues from the two together (adjusted for inflation) are expected to be flat going forward.