A nitric oxide (NO) detector was developed and integrated into the original carbon monoxide (CO) and hydrocarbon (HC) remote sensing system developed by the University of Denver. The system is capable of measuring the CO, HC, and NO exhaust emissions of thousands of on-road vehicles per day. Analysis of a typical field measurement in Denver shows CO, HC, and NO emissions have similar statistics which can be well represented by a gamma distribution. The fraction of NO high emitters tends to increase with age, apparently arising from deterioration of the emissions control system. This paper presents the inverse relationship between NO and either CO or HC emission.