Whether a train is pleasant for the passenger depends greatly on climatic conditions in the compartment. In a train with good lighting and good climatic conditions, one can travel not only safely, but also in comfort. The quality of the atmosphere is much more important on long journeys than for short trips. However, the cost of modifying these conditions rises sharply with passenger requirements. Warm-air heating and forced ventilation are at present considered sufficient for journeys of less than an hour. Modern suburban trains are therefore fitted with equipment of this kind. Long-distance coaches are today usually equipped with air conditioning systems which, in addition, include refrigeration facilities for cooling, and drying the air.