The state of the art in ride quality assessment is reviewed. A portable environmental measuring system (PEMS II) has been developed to simultaneously record variation in motion (in all six degrees of freedom), temperature and pressure for various segments of a ride. The results of extensive studies of passenger reactions to diverse vehicles are presented as a set of models relating human comfort ratings to environmental conditions, vehicles studied include aircraft (commuter planes, S-61 helicopter, Boeing 747, Concorde), trains (conventional and special purpose), buses, and cars. Limited data are available on marine vehicles. Models for aircraft involve vertical and lateral accelerations and noise levels; while models for ground based vehicles also involve roll rate.