Determining Transportation Expenses

The average transportation expense estimates are from the U.S Department of Transportation National Household Travel Survey (NHTS) and Internal Revenue Service (IRS) cents-per-mile estimate. The NHTS figures are used to derive a transportation figure estimating the basic costs of owning and operating a personal vehicle. These costs include traveling to and from work, school, religious activities and other necessary family and personal business. These costs do not include any social or recreational transportation costs a family may incur. In addition, public transportation costs are not included in our estimate. Public transit costs are excluded because only 5 percent of work commutes and 1.9 percent of total yearly transportation is attributed to public transit use. As a result, these calculations represent conservative transportation cost estimates for a family.

The data includes the average miles traveled per person in each Metropolitan Statistical Area (MSAs). A vehicle estimate is used versus a per person estimate to calculate transportation costs. This is because miles traveled in a carpool or in friends and relatives’ vehicles would not incur a cost to the family but would be included in a per person mileage estimate. By calculating costs using a personally owned vehicle, only miles traveled in the family’s vehicle are used in the transportation calculation. 

The NHTS estimates travel by five different MSA sizes, as well as for other areas considered rural. The average miles traveled per person are estimated using MSA estimates and applying them to 23 counties, while the remaining counties were given the rural estimate. In addition, the average miles are adjusted for the number of full-time workers, assuming all resident parents are full-time workers. For two-parent families, the costs are calculated by taking travel for work and non-social purposes for the first parent, and then costs of travel for work only for the second parent. The average mileage is then multiplied by the IRS cents-per-mile estimate. The IRS cents-per-mile estimate computes a standard mileage rate for business (non-social) purposes. Items such as depreciation or lease payments, maintenance and repairs, tires, gasoline, oil, insurance, and license and registration fees are included in this estimate.

Our calculations for one- and two-parent families are below. 
• Single-parent families: Average miles per vehicle/month/MSA * IRS cost/mile = transportation costs
• Two-parent families: (Average miles per vehicle/month/MSA * IRS cost/mile) + (Average miles to and from work only/month/MSA * IRS cost/mile) = transportation costs
 
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Children's Defense Fund Minnesota

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