102 Automotive Ergonomics: Driver–Vehicle Interaction
7.1.4.1 Effective Temperature
This is an early index, it is not a temperature as such, but an ‘arbitrary index of the
sensation of warmth experienced as a result of air temperature, humidity and air
motion. It combines these three factors into a single value’ (Yaglou, 1927). Its under-
lying principle is that changes in any of the three factors may vary greatly as long as
the combined effect remains the same. Hence, an increase in air temperature must
be compensated for with a corresponding decrease in relative humidity or increase
in air velocity. Effective temperature does not take into account radiation, although
a correction can be made by using a 150 mm black globe thermometer (CET