"..We could also subsidize riders ..."
Funny.
"...if we can get funds for.."
Taxes
Not necessarily....
Traditionally, infrastructure construction has often been funded through the issuance of tax-free bonds... and the debt is repaid via revenues from tolls/fares.
"..We could also subsidize riders ..."
Funny.
Many municipalities deliberately choose to subsidize mass transit because it is believed to benefit local businesses and merchants (much the same way as providing "free" municipal parking lots.)
IMHO, it will probably be unnecessary to subsidize mass transit riders in many locales due to rising fuel and insurance costs and tolls imposed on highways (because legislators are too afraid to increase the gas tax to cover highway maintenance costs.)
That, and simply because traffic congestion and gridlock is a PITA.