Here's a great website to help you calculate what the true cost of your commute is. Check out the Commute Cost Calculator at Commutesolutions.com.
You simply input the distance of your commute, your gas mileage, and use their guides to calculate the cost per mile for depreciation, repairs, wear and tear. It also asks for the monthly cost of your auto insurance. But I leave that blank. They also ask for your monthly car payment. That, too, I left blank. Even if I took the bus to work everyday, I'm still going to have a car and pay for auto insurance.
So, what was my total cost?
Based on a 40 mile round trip commute, 22 working days per month, 26 miles per gallon, $3.30 per gallon, repairs and such at 8.5 cents per mile, and depreciation at 16 cents per mile, my commute comes out to $327.29 per month. Yikes! That's too much.
Here's the little secret. It's not because of increased gas prices. I changed my assumptions to $2.00 gas. My monthly cost drops to $283.29. Not nearly as much as you would think given the non-stop media coverage of gas prices.
There are a ton of other commute cost calculators if you search google, but I found this one to be the best. It allowed you to make adjustments for the depreciation, repairs and such, but gave you recommended guidelines based on the type of car you own. Some of them are regional, and have inputs for tolls and other local costs.
Pretty interesting stuff. By the way, my Fiancee and I carpooled today! That saves us about six bucks.