From an article by Doug Hissom posted on OnMilwaukee.com:
We can each save more than $8,000 a year by taking mass transit says an American Public Transportation Association report. If gas prices stay in the $3.90 a gallon range (unlikely at this point) the association predicts a person can save around $672a month — more than the average household spends on food.
Among the top 20 cities with the highest ridership, Honolulu wins the savings title, amounting to $8,703 a year, Minneapolis riders saved about $8,104 a year by taking the bus and Chicago amounted to $8,100. Milwaukee did not make the list.
The association says its study is based on the assumption that a person making a switch to public transportation would likely purchase an unlimited pass on the local transit agency, typically available on a monthly basis.