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Trips per person X miles per trip = VMT

The Vehicle Miles Traveled (VMT) per employee calculation combines the the number of people who share the trip (trips per person) with the length of the one-way commute trip (miles per trip). It reduces the person trips for employees who use high occupancy modes as shown at right.

For example: Joe commutes to work five days each week; he drives alone three days and carpools with a friend the other two days each week. His one-way trip is 10 miles.

3 drive-alone trips + 2 two-person carpool trips X 10 miles per trip = VMT
5 potential trips per person

then,

3 drive-alone trips + (2 x 1/2 trips per person) X 10 miles per trip = VMT
5 potential trips per person

then,

4 trips per person X 10 miles per trip = VMT
5 potential trips per person

finally,

4 X 10 = 8 Vehicle Miles Traveled
5

Most employer programs will not affect the length of an employee's commute trip (the "miles/trip" portion of the VMT per employee equation) . But, employer programs can and do influence commute choice (the "trips/person" portion of the VMT per employee equation).

"Trips per person"

  • A drive-alone trip (also includes one-person motorcycle and drive-on ferry trips) = 1 trip
  • A two-person carpool = 1/2 trip per person   
  • A three-person carpool = 1/3 trip per person
  • A four-person carpool = 1/4 trip per person
  • A five-person carpool = 1/5 trip per person
  • A six-person carpool = 1/6 trip per person
  • Vanpools of less than seven but more than two occupants are counted as carpools (see above).
  • Vanpools of seven or more and transit (bus, train or walk-on ferry) = 0 trip per person
  • Trips not made because of teleworking and a compressed work week schedule and all non-motorized trips (bicycling, and walking) = 0 trip per person.