Many states limit gas tax revenues for highway purposes only.
In some places, bridge tolls are used to subsidize local transit. However, this benefits motorists since the traffic congestion becomes terrible without transit carrying many people (as have happened). Examples are PATH trains to NYC, PATCO trains to Phila, and TBTA bridges in NYC.
The incremental cost to subsidize such existing transit lines is far cheaper than building new river crossings. When PATCO opened in 1969, the Delaware River Port Authority published numerous reports explaining the money and time savings PATCO offered.
Sorry, but it is a fact, not a lie. Transportation corridors used to be taxed, in some cases (e.g. railroads) at very high rates. As an example, In NYC in the 1950s, the Pennsylvania Railroad was paying over $1 million a year just for Penna Station. However, at the same time the competing Port Authority bridges and tunnels paid zero taxes. Historically, the PA would be liable for taxes, but they went to a great deal of trouble to secure an exemption. The book "Empire on the Hudson" details all this. All over the country commuter railroads paid steep property taxes on their facilities while newly built expressways were tax free. This was an effective cost subsidy to motorists.
As to the issue of roads not "generate any demand for the last three", plenty of us have no children yet we all must pay property taxes for schools.
When a highway is built, the land goes off the tax rolls and the rest of us have to make up that shortfall. That should be obvious.
In any event, roads do require substantial public safety services such as police/fire/resue. Someone has to paid for them. The taxation varies by state, but in many places (like mine), it is is paid for by local property taxpayers. Note that highways are ten times as dangerous as trains and require far more services per passenger mile than trains do.
As to the term "leftist", the support of transit is not a 'left' or 'right' issue, it is one of giving people the safest, fastest, and cheapest way to get around. In addition, developed areas have run out of land to bulldoze for more highways. Automobiles pollute big time. Or, perhaps you are saying only those on the "left" are concerned about pollution?
The interest on bonds issued by government agencies are exempt from taxes. The bonds issued by railroads and the private transit companies were taxable. The tax exemption allows bonds to be issued at a lower interest rate which is a savings not available to the railroads. In addition, bonds from govt agencies, even if not officially guaranteed, are in essence guaranteed none the less because a state doesn't like to have defaults. It is extremely rare for a govt bond to default for that reason. This also helps lower the interest rate.
The above ignores the fact that millions of people ride transit. Amtrak, with all its flaws, is carrying a record number of passengers. As stated above, in developed areas transit does free up critically needed highway space.
When quality transit is offered people will ride it. When old lousy systems were fixed up, riders came back. The buses, subways and commuter trains in the NYC metro area has ever increasing ridership. New subways and rail lines in car-loving California (San Fran and L.A.) carry many people.
I am reminded of the time Mayor Daley suggested 'municipalizing' the Commonweath Edison Company. Their rationale was 'people want to get fair prices and inexpensive electric service.' Edison got up in Daley's face and said, "So ... the politicans who run the Chicago Housing Authority, the public schools and the Transit Authority should now take over the nuclear generating stations as well?" And Edison kept on saying that publicly, via television and radio. Major corporations made plans to move out of town; saying that the mere thought of City of Chicago in charge of necessary electric power scared the Bejesus out of them. Mayor Daley meditated on that for a while and finally backed down. PAT]