City comptroller and mayoral candidate William Thompson is urging the Ravitch Commission today to push for a revival of the commuter tax to help stave off an MTA “doomsday scenario,” expected to unfold next spring unless the agency gets help.

Thompson is also advocating a new surcharge on vehicle registrations in 12 counties served by the authority, which he estimates would raise an additional $1 billion a year for transit. As explained by Thompson’s chief economist Frank Braconi on WNYC’s “The Brian Lehrer Show” this morning, the surcharge, like the existing state fee, would be based on vehicle weight, and would result in an average fee of $200. Currently, motorists pay $30 in city registration fees every two years.

Naturally, Braconi was peppered with questions from indignant motorists, one of whom asked why he should “subsidize” transit. Braconi’s reply:

“There are many hidden subsidies of auto drivers … But the truth is that mass transit [riders] subsidize auto drivers in many ways. For example, the fact that we can park free on our streets for the most part … But the fact is we are all one city, and we all benefit from mass transit. Parking and driving would be virtually impossible in this city, it would be so congested, without a functioning mass transit system, and vice versa. I think mass transit users benefit that there are automobiles to deliver goods, and taxis, et cetera, et cetera … [Drivers and transit users should] realize there is some fair way to distribute the costs of making the city work properly.”

Fielding a call about motorists dodging the fee through registration fraud, Braconi said that residential parking permits are included in Thompson’s proposal.