A Remote Sensing Device (RSD) was used to measure on-road emissions of carbon monoxide (CO), hydrocarbons (HC, propane equivalent), and carbon dioxide (CO2) from vehicles as they entered and exited a centralized Arizona Inspection and Maintenance (I/M) lane conducting a steady-state dynamometer test. Approximately 16,000 RSD measurements were collected and matched with I/M records from 9,000 vehicles. The RSD demonstrated approximately a 90 percent success rate in recording emissions and license plates. When moderate RSD pass/fail standards were applied to the data, approximately 41 percent of the 1981 and later I/M failures were identified based on a single RSD measurement. When the minimum reading from two RSD tests was used, only 20 percent of the I/M failures were identified. However, virtually all of the vehicles that failed two RSD tests were I/M failures.