**Curious about how the calculator works, and what underlying assumptions we’ve made to arrive at our totals? Here are the details:**

**Under personal financial cost:**

For driving and carpools:

We multiply the miles in the trip by the sum of the following:

An average of 58.5 cents per mile of personal automobile ownership and maintenance costs. This is an average for medium-sized sedans travelling 15,000 miles/year, according to AAA’s 2012 Your Driving Costs.

The amount you said you pay for gas multiplied by the miles per gallon fuel efficiency you entered. If you ask to use the default, we used $4.03/gallon and 21 miles/gallon, NYSERDA’s Upstate NY average for September 2012, and the average from the USEPA for passenger vehicles, respectively.

Any amounts you entered for tolls and parking.

For vanpools:

The Capital Region first-half 2012 average cost of a vanpool divided by 8 for 8 passengers, then divided by 21, assuming you work 5-day workweeks.

Any amounts you entered for tolls and parking.

For local buses:

The CDTA cost for one trip and the cost for a day pass, which would allow for transfers.

For commuter buses:

An estimated $4.40 for a one-way commuter bus ticket in the Capital Region

The cost to drive to a car to the bus pick-up location, based on an assumed 3-mile drive to a park and ride lot.

For biking:

Average cost of bicycle-related gear ($350/year) divided by the average number of miles ridden (3,000/year), copied from Arlington VA’s commute calculator

For walking:

Average cost of walking-related gear ($120/year) divided by the average number of miles walked (1,500/year), copied from Arlington VA’s commute calculator

### Under Emissions:

For driving and carpools:

19.59 lbs of CO_{2} per gallon of gasoline burned divided by the miles per gallon fuel efficiency you entered multiplied by the miles in the trip.

For vanpools:

19.59 lbs of CO_{2} per gallon of gasoline burned divided by 20 miles per gallon average Capital Region vanpool fuel efficiency multiplied by the miles in the trip

For local buses:

22.44 lbs of CO_{2} per gallon of diesel burned divided by a CDTA average of 4.41 miles per gallon and divided by a CDTA average load (Jan-June 2012) of 13 passengers.

For commuter buses we add together:

19.59 lbs of CO_{2} per gallon of gasoline burned divided by the fuel efficiency you entered, and multiplied by an average of a 3-mile drive to a park and ride lot.

22.44 lbs of CO_{2} per gallon of diesel burned divided by an average of 5.35 miles per gallon and divided by an estimated load of 23 passengers, which are both 2012 averages of the Northway Express service.

For biking and walking:

We recognize that humans emit carbon dioxide when they exhale, but we have considered it small enough to omit here.

### Counting Calories:

We recognize that you burn calories even when just sitting in car, van or bus, but we consider it small enough to omit here. We’re counting physical effort to walk or bike as follows: To catch a local bus, we assume you’ll walk 0.3 miles, burning 88 calories per mile. When walking we use that same 88 calories per mile figure, and for biking we figure on 42.7 calories per mile.