Bostonians can pocket $12,632 this year by switching from their trucks to the T; New Yorkers can save $12,589 by riding the subway instead of the highway. Car-loving Los Angelenos can save $738 a month, Washingtonians $811, and Clevelanders $774. Or so says the latest monthly savings report from the American Public Transit Association, released yesterday. The report arrived at its local figures by factoring the cost of a monthly transit pass in individual cities against average fuel and parking costs over the same period.

The national average savings of $8,691 is based on the May 5, 2009 average gas price of $2.079 and the national average cost to park in an unreserved place in downtown business districts — $143 a month. The cost of driving is calculated using a AAA formula that factors in both fixed costs, like insurance, registration and financing charges, and variable costs like fuel and maintenance.

The rub is that in calculating the overall savings, the researchers also presumed that the person switching to public transit would give up one car. Not what the struggling carmakers of America want to hear, of course. And those facing looming fare increases in New York City and cutbacks in places like St. Louis might decide that the convenience of driving is something they can’t give up, even in hard times. Even so, the report might carry more weight than before, given the current economic climate. Will you make the switch?