This report covers the efforts to make use of three cycles, known as Class II (6,001 to 10,000 GVW), Class III (10,000 to 19,500 GVW), and Class IV (19,501 and above), to survey the emissions from a wide variety of gasoline powered vehicles. The principal emissions of interest were CO, unburned HC, and NOx and were obtained on a mass, lb/mi basis. Emissions from selected vehicles were studied in detail to correlate the constant volume to the servoproportional and continuous methods. Emissions were then acquired from over 150 vehicles using a specially prepared truck size version of the PHS developed constant volume sampling system. All results are summarized by class and are rank-ordered from 'low to high' by CO, HC and NOx. By equally weighting the emissions, each vehicle's overall contribution was determined. Attempts were made to relate the amount of emissions to year, make, mileage, etc. The results for the same vehicle operated under two applicable cycles were compared.