Enter the combined mileage driven annually for all automobiles under Miles/Yr in the Automobile field of the Options panel.
Please note: To return to the default value for a particular field, click the 
button in the modified field. To return to the default values for all fields, click the 
button at the top of the Options panel.
To estimate the cost associated with leasing a vehicle, one approach is to enter a value of 0 for Number Owned and Total Value and include the relevant Miles Per Year estimate. The resulting value in the Transportation field is an estimated cost of leasing a vehicle.
See Two City Comparison - Background for more information.