How much is your vehicle costing you at the pump? Photo by Sanford Kearns.

The American Public Transportation Association (APTA) released its monthly "The Transit Savings Report" detailing how riding public transportation on average saves money. The report found that individuals save $9,515 annually (up by a few hundred dollars from this time last year) and up to $793 per month based on the average national gas price on November 8, 2010 ($2.85 per gallon, reported by AAA) and the national unreserved monthly parking rate. This monthly savings is up 3.5 percent compared to last year.

"The Transit Savings Report" calculates the average annual and monthly savings for public transit users and examines how an individual in a two-person household can save money by taking public transportation and living with one less car.

The top city for transit savings is New York City, with calculated savings of about $14, 000. In Los Angeles, savings were $10,000 and in Washington, D.C. savings were around $9,500. (View a full list of cost savings in the cities with the highest number of transit users here.)

APTA calculates the average cost of taking public transit by determining the average monthly transit pass of local public transit agencies across the country. The information is based on the annual APTA fare collection survey (link) and is weighted based on ridership (unlinked passenger trips). The assumption is 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.

A representative of APTA said that in Washington, D.C., for example, the association uses the cost of four weekly passes for its calculation "because based on the parameter in which we have to work that's the closest estimate we can get to what someone would spend in a month period… " The cost of Washington D.C.'s weekly passes, however, includes only Metrorail for its fare of $47, but many District residents take Metrobus or the Circulator to transfer to Metro—costs that would not be included in APTA's calculation of public transit costs.

This average monthly transit fare is then compared to the average cost of driving, according to a 2010 AAA formula based on variable and fixed costs of driving. Variable costs include the cost of gas, maintenance, tires and parking, which is $161.56 per month in a downtown business district, amounting to an average of $1,939 in a year. The fixed costs include insurance, license registration, depreciation and finance charges. According to APTA, "the comparison also uses the average mileage of a mid-size auto at 23.4 miles per gallon" and the most recent price for self-serve regular unleaded gasoline.

It seems, however, that there are a number of costs to the public transit user that the report fails to include in its methodology would be useful to paint a clearer picture of the cost of driving versus public transit use.  Public transit users pay for the following in addition to public transportation: bikes, cabs, Zipcars or car rental. Although they are not forms of public transit, these additional transit costs are significant and probably even higher for a family doing activities like grocery shopping or traveling in bad weather. In addition, there may be those people who may not feel safe or comfortable and elect to take a cab frequently. So the savings are perhaps not quite as great as the report emphasizes.

In terms of the monthly and weekly pass calculation, do you think APTA's average cost accurately covers the transportation cost for your city? This report makes me want to keep a detailed account of how much I am spending on transportation, including bike parts and cab fares to better track the cost of a car-less existence.