An overview of the development of a NASA ride comfort model is presented. A new instrument is described, the Ride Quality Meter, which incorporates the NASA-developed model to characterize ride comfort based upon measurement of vehicle interior noise and vibration. The meter is a portable unit which provides real-time estimates of passenger ride comfort during actual vehicle operations. It provides the first known capability to directly sum the effects of noise and vibration into a single objective comfort index. The meter has been shown to be applicable to passenger cars, trucks, buses, trains, aircraft, and a wide variety of special purpose transportation systems. Data is summarized demonstrating application to automobiles and helicopters. The meter has been shown to perform as a reliable and accurate passenger jury.