The number of people, including the respondent, who usually rode together to work in a car, truck, or van during the reference week ("last week"). Riders who rode to school or some other nonwork destination were not included. Vehicle occupancy vas asked on a sample basis for persons at work last week who indicated the use of a car, truck, or van in the means-of transportation-to-work question.

Data are reported in terms of categories like "Drives alone," "In 2- person carpool," "In 3-person carpool." etc., and/or as an average: persons per private vehicle. In the calculation of means or aggregates, 8 is taken as the average value of the open-ended category "7 or more." Note that these data are presented in terms of the number of persons in carpools of a given size, not in terms of the number of vehicles or carpools. To approximate the number of vehicles accounted for by these statistics, divide the number of persons who went to work by car, truck, or van by the mean number of persons per vehicle; to approximate the number of carpools, the subtract number of persons driving alone from the derived number of vehicles.