I assume you're referring to reimbursement rates for use of a personal car for work purposes... those numbers always seem very high given actual gas cost and depreciation
Those reimbursement rates are based on the actual costs of an average car. Yes, including deprecitation. The last Civic I had depreciated $12,000 in about 120,000 km so that's 10 cents/kilometre right there. Gas ... well that's a factor. Throw in insurance, maintenance, etc. Better yet, throw in accidents ... you don't get those with the car parked at home. I loved the Ikea trip that cost $550 for a $50 table after a hit-and-run and losing $500 deductible (and that's ignoring the hours of time spent on it between towing, visits to body shop, and the police investigation). Though "average" seems to be better than I buy. About 7-8 years ago I had to do the real calculation for my taxes, and it came in at about 25 cents to 30 cents per kilometre (it went up after I bought a new car, and the depreciation increased). Probably was higher more recently with the gas prices, but that's over for now.
We live near Woodbine station so it's only about 9 km to downtown, so gas probably costs less than a dollar. We plan to keep the car until it falls apart and don't put excessive mileage on it, so the net depreciation is probably zero for an extra trip. Also as you say, we can be downtown in 15-20 minutes off-peak vs. 40 minutes on the subway. When you factor the value of our time, driving is a no-brainer.
I live not so far from Woodbine station. 40 minutes on the subway? You exaggerate a bit. Google maps says 23 minutes from Woodbine to Dundas mid-morning off-peak ... same on Saturdays.
Trips to places outside of downtown (where parking is free or cheap) favour the car even more... we often drive to restaurants down in Leslieville because street parking is free after 6PM. $2.80 each for a one-way 2 km trip is completely ridiculous.
I don't drive to restaurants, simply because I like to have a drink with dinner.
This is the kind of reason that most in this situation have a Metropass. Given that the cost of a Metropass is the cost of 43 tokens (don't forget the 15% tax credit on passes), the Metropass is pretty much paid for with 20 days of work in a month. For extra savings, I've got an annual subscription, so it's paid for in less than 40 trips per month.
At least once a week or so I stop somewhere for something on the way home. There always seems to be a medical appointment every month (well, it always seems to be 3-4 in one month and none for months ...) that takes 2 trips. Once every couple of weeks my wife takes it and I use tokens, and she does a big shopping spree up and down Danforth. It's hard not to have the required 43 (or 40) trips in a month to make it pay off. One month in the last 7 years I ended up out of town for 3 weeks, and it only got about 20 rides. Another month I sold it to a friend at cost (which they thought was a bargain at the discounted annual price!).
Quite frankly, I don't really want the hassle of driving downtown, and then parking. Though there are spots that are difficult to get to on transit. Leslieville. Even due south to Queen is a pain if your mid-block between two routes. Kingston and Victoria Park. So then occasionally the car comes out. And across-town late evenings ... though even weekends are becoming increasingly painful to drive.
