So many of us drive all over the place and think we have no other choice. But if you look at how much you could save if you dropped the car, choices can really open up.

The American Public Transportation Association (APTA) just put out a report showing that the "average person" in 16 of 20 large US cities would save over $10,000 a year by using public transit instead of driving. Across all 20, the average was $10,181. In New York City, the average savings based on APTA's assumptions come to $15,041.

As many of you know, I've been living car-free for 10 years. The key factor that has enabled that is that I've always chosen places (cities and neighborhoods within cities) where I could easily and enjoyably get around without a car. I went car-free for two main reasons: 1) I wanted to live in a more climate-friendly and overall environmentally friendly way, and 2) I discovered that I enjoyed biking for transportation much more than I enjoyed driving for transportation. I was well aware that biking and using transit would also save me a ton of cash, but that wasn't my motive.

However, I wish that I had decided along the way to track how much more I probably would have paid for transportation if I had decided to live an alternative life in probably different homes and drive almost everywhere. I know the savings have been considerable, but I really have no way of coming up with a legitimate estimate.

Thomas Hawk/CC BY-NC 2.0

If you're still driving everywhere, the good news is that you still have the chance to do so! If you decide to make the switch, I really encourage you to track your estimated monthly savings. You'll feel great in 10 years when you take a look at how much you've saved.

Of course, some of you are in a situation where you could start biking or taking transit where you currently live and could calculate right now how much you'd probably save. For some of you, I'm sure that you wouldn't really be able to bike or take transit unless you moved, but this is something to keep in mind in case you ever do. At the least, however, you could simply calculate how much you spend driving and consider if you couldn't get a nicer place in a nicer location with those savings.

I was quite shocked last week to see an article about this exact topic in Reuters. It really wasn't a typical Reuters story, but it was a great one. As an example, it focused on a 59-year-old from Elon, North Carolina, who had previously had a 2.5-hour commute (each way) for 4 years from the mountains of Caldwell County to Chapel Hill. In gasoline costs alone (forget oil changes, maintenance, repair, insurance, time/opportunity costs), she estimated that the commute cost her $43,000.

"I always thought it would make me sick to find out," she says. "And it did."

I think this is a topic to come back to another day. There are so many interesting angles to this. But, for now, if you are interesting in looking at or playing with some numbers, below are estimated average savings in 20 large cities for an individual in a two-person household who decides to drop the car and take public transportation. Following the list are some details regarding APTA's assumptions.

APTA/Screen capture

APTA calculates the average cost of taking public transit by determining the cost of the average monthly transit pass of local public transit agencies across the country. This information is based on the annual APTA fare collection survey 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 public transit agency, typically available on a monthly basis.

APTA then compares the average monthly transit fare to the average cost of driving. The cost of driving is calculated using the 2013 AAA average cost of driving formula. That formula is based on variable and fixed costs. The variable costs include the cost of gas, maintenance and tires. The fixed costs include insurance, license registration, depreciation and finance charges. The comparison also uses the average mileage of a mid-size auto at 23.1 miles per gallon and the price for self-serve regular unleaded gasoline as recorded by AAA on May 28, 2014 at $3.65 per gallon. The analysis also assumes that a person will drive an average of 15,000 miles per year. The savings is based on the assumption that a person in a two-person household lives with one less car.

In determining the cost of parking, APTA uses the data from the 2012 Colliers International Parking Rate Study for monthly unreserved parking rates for the United States.

To calculate your individual savings, with or without car ownership, go to www.publictransportation.org.

