Measurements of comfort in vehicles

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Abstract
Recently, several factors have contributed to an increase in interest in the evaluation of comfort experienced by passengers in vehicles. Due to rising mobility, the time that people spend in vehicles has grown substantially. The criteria applied by consumers have changed on account of generally heightened expectations, resulting in a growing demand for enhanced ride comfort. Also, there are marketing factors, from the car manufacturers' point of view, because differentiation between models in the same market segment is becoming more difficult to establish on grounds of performance or aesthetics. The comfort experienced by humans in a given environment can be classified as a subjective assessment, because it is possible to find a considerable variation in responses of different people to the same situation. Nevertheless, the factors on which the opinions of people on comfort level are based are physical variables that characterize the surroundings, e.g. temperature, air velocity, acceleration, and light intensity. So, the first step in any assessment is to list the different kinds of stimulus that can be detected by human senses and judged a cause of annoyance, leading thus to a sensation of discomfort. In the case of passengers riding in vehicles, the following are the main aspects that should be considered: temperature, air quality, noise, vibration, light, and ergonomics. Many different measuring and evaluation methods have been developed to study the comfort of occupied spaces, involving one or more of the aforementioned stressors. Besides discrete measured values of relevant physical parameters, comfort indices related to human sensitivity and weighting the influences of different variables have also been built in for each kind of stimulus. Subjective assessments from evaluation panels are also extensively used. Because researchers are conscious of the importance of the interaction between the passengers and the environment, various measuring mannequins with the capability of simulating some human functions, e.g. thermal regulation or breathing, have been developed.