It often asserted that cyclists don't belong on the road because they don't pay the gas tax, or that they should start to pay for it like drivers do. Frequent commenter SJE points out that the Maryland DOT 2014 budget overview shows - again - how wrong this is.
In 2012, gas tax brought in $734M, out of the total $2,830M revenue. MDOT spent $2,864M. So the 2012 gas tax covered 25.6% of MDOT expenditures. Barely a quarter. Its certainly not a golden good funding other activities, as some assert.
Does it even cover roads? Lets take out aviation, ports and WMATA costs (bikes are so small they don't even make it) which account for 31% of MDOT costs (see page 13). Lets say 33%. So, 25.6% of in the income divided by 66% of the costs: Gas tax therefore covers about 39% of road-related costs paid by MDOT.
Where does the money come from then?
Top source was "corporate income, registration, misc MVA fees" ($795M). "Titling taxes" were $632M. So the state is already not collecting most of its transportation income as a user fee (gas tax) but through various other taxes on other activities. You do far more to pay for the roads when you buy a car than through the gas tax.
Estimates for 2103 put the gas tax at 18% of MDOT revenue, and so the rise in gas tax is still not covering a whole lot of MDOT budget.
Car owners do cover the majority of the budget for MDOT, but as is often noted - most cyclists are also car owners. In fact the more a car owner users their bike instead of their car, the more the subsidize everyone else. And even non-car owning cyclists pitch in through other taxes (enough to cover their share of the road I suspect).