BTW, I know the calculator no longer works.  I sold the Bicycle Universe site a few years ago (to buy a Pac-Man machine).  The calculator worked at first after migrating to the new owner's host but now it's not for some reason.

I increased the per-trip costs for taxi and carshare, and decreased the frequency for both.  I also doubled the figure for bike maintenance.  I know these new figures still don't work for everyone, but *no* numbers will work for *everyone*.  Everyone's situation is different, and that's why the calculator lets the user enter their own numbers. :)

The insurance/license/registration defaults are from AAA's study of average vehicle costs in the U.S., as noted under the calculator.  Again, it's not the same for everyone, and everyone can enter their own figures.

If you want to account for replacing your bike every X years, just add that amount to the Annual Bike Maintenance field.  (e.g., $400 every 10 years is +$40 into bike maintenance).  This is nearly a negligible effect on the bottom line, though.

You're right, I assumed that the car is replaced as soon as it's paid off.  I'm going to keep it that way for simplicity because the calculator is already big (and complicated) enough, but I went ahead and added a note about this to both the pop-up help and the notes under the calculator, noting that if someone doesn't replace their car right away they can account for that by entering a lower figure for their yearly interest+depreciation.

On the gas cost, I think most people have a better idea of how much they spend a week on gas than the number of miles they drive in a year and the actual (real-world) mpg of their car.  It's certainly easier to have one field instead of three.  This is another area where I'm gonna take a shortcut to try to avoid making the calculator unwieldy.

The results are absolutely inflation-adjusted!  Or rather, they don't need adjustment by default, because I assume we spend the same amount every year, without increasing it for inflation.  I went ahead and noted that the calculator does give inflation-adjusted results.

I changed the default interest rate to 6.72%, which is the annualized long-term return of the U.S. stock market, adjusted for inflation.

And yes, I made a huge error in the interest calculations.  What was I smoking?  I fixed that.

Finally, let me share a reply that someone accidentally sent to the list rather than here:

Thanks again for all the constructive help!

-- edit, I assumed I would car share or take a taxi or rent a car.  If I went ENTIRELY bicycle, and never used a car under any circumstances I would obviously save more.

The "car cost"/year is pretty close, assuming I keep my car for seven years.  (I hope to keep it longer, but we'll see.)

As a 40+ year old married man who hasn't made a claim in years, I pay $31/month for full insurance coverage on my fairly new compact car -- pretty far from $79/year.

Your registration/taxes is *way* high for Texas.  I pay about $70/year for registration and $30/year for inspection.  No taxes (other than sales tax on new car, but that's covered in it's price.)  Other states tax cars more thoroughly, but not here.  (I imagine you just used the AAA figures, so that makes sense.)

I spend next to nothing on parking, but that's just me ...

On the bicycle side ...

You assume that the $400 bicycle will last 35 years and that the commuter will only have one and it will never be stolen.  That seems overly optimistic :)
(Yes, some people have had bicycles last 35 years of daily use -- but some people have cars that have as well, and that's certainly not taken into account on the left side.  And it shouldn't be -- it's the exception rather than the rule.)

$50/year will barely cover a professional tune-up, let alone new tires and such.

And you've made a huge mistake on the interest calculation.  Using all your default values, a car will cost $275,065 over 35 years, and a bike $74,985, and it says "Total saved over 35 years if invested @  6% interest: $1,540,741".

However, this calculation seems to be based on compound interest on an initial investment of $200,080 over 35 years, when in fact this $200k will be building up over time.   i.e. your calculation seems to be based on somebody giving you $200k on day one, and you put that in your 6% savings account and wait 35 years, when the reality is that you'll get an average of $5742 (less the first year because you bought a bike) to put into that account each year, so the amount gained from interest will be roughly half of what you said.

The interest calculation also seems to think that the bike is purchased at the end of the 35 years rather than the beginning?  (If you change the figure from $400 to $0, that means you saved $400 more the first year, but you don't seem to get compound interest on that $400.)

And of course, the value of this $1.5 million (or $0.85 million once the interest is done properly?  I haven't pulled out a calculator) 35 years from now will be a lot less in 2011 dollars.  Really, throwing compound interest and large periods of time into this calculation simply muddies the waters, as many of these figures will be changing massively over time -- I doubt gas is still $4/gallon 35 years from now, for example.  And 35 years ago, small cars didn't cost $20,000 either.

Hell, I think 35 years from now most cars won't use fossil fuels at all (electric seems likely), and private cars might just be a luxury item for the very wealthy.  And insurance will be next to nothing as most motor vehicles will be computer controlled and almost never crash :)  (at least that's my take on it, we'll see how accurate it is.  35 years is a long time.)

The calculator would be more "honest" if you did away with the interest calculation entirely.  But if you leave it, mention it as "money for retirement".  (And you'd only pay taxes on the interest part, not the money saved.)

I'd suggest a few changes to the defaults --

--- rather than ask for a dollars spent on gasoline/week, you should ask for miles driven per year, car mileage and price of gas per gallon and calculate from that.
-- a new bicycle every four years (the car figures seem to be a new one every 8 years or so?)
-- $100/year bicycle maintenance (remember, this bike is going to get a lot of use)
-- fewer taxi rides, but they cost more

I had saved every receipt for every single repair, oil change, tune up, and tire change.   I totaled these and added in what I had payed for insurance.  I had to make an estimate on the gas, so I went with a fairly conservative number.

In the 16 years I owned that car it cost me at the very least $175,000.  I think the number may actually be closer to $200,000 because I was so conservative on the fuel estimate. I just wanted a low total estimate.

I sure wish I had invested that money instead.  Most of that time I was married and we had another car anyway.

Actually, I feel a bit sick to my stomach at the moment.

I do not think you can get a cab for $6 from anywhere to anywhere, it is usually $20-50

I agree, but I also think the default numbers in terms of how _often_ you have to use a cab are pretty pessimistic.

The only times we've had to use a cab are things like...

- doctor's appointment for a medical problem that prevents cycling [back/knee issues are no fun]

- backup ride home after mechanical failure [outside car2go range, or account not working and Austin office closed]

- going on vacation, missed bus to airport.

...these are all pretty rare events. If my wife had a foldable/packable bike like I do (and a trailer for carrying a suitcase... that packs into the suitcase with the bike!), we could have just biked to the airport and avoided the 3rd one altogether. So -- price-per-trip is far too low, but number-of-trips is far too high. (A similar thing is true on the carshare charges -- I spend closer to $15/trip on car2go, but that's something I do less than once a month).

One big thing the default values missed for me was mass-transit charges -- I take the train to (within a few miles of) work every day, and the everything-included CapMetro month pass adds up over time -- and the bike-maintenance costs were lowballed compared to what I see in practice -- but the numbers still came to about $1.2M savings.

The much bigger thing it missed, though, is the cost of the new bike habit -- the car numbers assume a new vehicle every time the lease or loan runs out, after all. Factoring *that* in makes my hankering for a shiny new custom-frame internally-geared folder (but belt-drive this time!), or one of Elliot's custom stokemonkey-assist Xtracycles, or [...list goes on...] look downright fiscally irresponsible.

Here you go:  Biking vs. Driving Calculator