Table 1

Summary of participant characteristics

Smokers recruitedSmokers returning monitorsNon-smokers recruited and returning monitors
Number24175
Age, mean (SD)39 (11)38 (12)37 (11)
Sex, % male334760
Education (%)
    High school (<13 years)263120
    College + (⩾13 years)746980
Vehicle activity
    Days/week driving vehicle, mean (SD)7 (1)7 (1)5 (2)
    Hours/day driving vehicle, mean (SD)2 (1)2 (1)1 (1)
Active smoking (%)
    Current smoker1001000
    Smokes daily9694
    Smokes less than daily46
Smoking in vehicle (%)
    Every day8376
    Some days1724
    Do not smoke in the vehicle100
Vehicle size* (%)
    Compact/small423560
    Mid-size/large586540
Number of passengers usually occupying the vehicle†
    0585840
    1171240
    ⩾2253020
Number of children usually occupying the vehicle
    0717160
    ⩾1292940
Have rules in car that restrict smoking (%)7982100
Smoking rules/restrictions (%)
    Not allowed in vehicle00100
    Allowed only with use of ventilation2021
    Allowed only without passengers157
    Allowed with ventilation and no passengers6571
Driver opinion (%)
    Smoking poses a health risk to passengers100100100
    Being unable to smoke in the car would help you to quit smoking5353
    Vehicles should be smoke-free on a voluntary basis939360
    Vehicles should be smoke-free by regulation7760
  • *Vehicle types included compact and midsize cars, minivans, and sport utility vehicles.

  • †Includes both children and adult passengers combined.