As the projected operating deficit at the state-run Metropolitan Transportation Authority increases by as much as $650 million, to nearly $2 billion, MTA board members have gone to Albany today to continue their lobbying for the Ravitch plan.

The proposal includes an idea to raise $600 million annually via a new toll on the currently free East River and Harlem River bridges, mostly to raise money for capital projects.

In theory, a toll on the bridges isn’t a bad idea. People would pay for the bridge in money, not in traffic-waiting time. Current economic circumstances are making it a bad idea right now, though.

In recent months, people have proven to be much more sensitive to increases in prices than they were a few years ago. Last November, even after gas prices had declined, traffic on the MTA’s bridges was down 5 percent from the previous year, as people switched to the subway. And in Indiana and Virginia recently, drivers have surprised the private operators of toll roads by staying away from their roads to avoid drastic hikes in tolls, helping destroy the private operators’ business model.

If the MTA imposes a new toll of several dollars per trip, it’s impossible to know right now how many people would just choose to stay home or find another way of getting around instead. Yes, part of the point of the tolls is to reduce congestion — but not by too much.

And Fitch Ratings warned just weeks ago of the MTA that “loss of ridership and traffic due to city and regional job losses cold have an impact on bridge and tunnel operating revenues greater than anticipated.”

A higher-than-expected sensitivity to new tolls would hurt Manhattan retailers.

But it would also hurt the MTA, which would have spent capital money on the infrastructure to collect the tolls and have taken on a new financial burden to maintain the bridge (currently done by the city) without getting the return expected.

More worrisome MTA news: the authority said today that transit ridership fell in January, 2 percent year on year, for the first time in six years.

The MTA only has so much room to hike subway and bus fares in this kind of economic environment before people just stay away.

Lower ridership is first bad for the city’s economy — but it also won’t help the MTA reduce its costs, which are massively fixed.

Albany needs to get serious about what to do about the MTA — time is running short.