Infrared thermography in applied road climatological studies

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Abstract
The aim of this paper is to describehow infrared thermography is used to analyse variation in road surface temperature during clear calm nights. Having knowledge of surface temperature variations along road stretches makes it possible to give an accurate survey of the risk of local slipperiness. The infrared equipment used is an Agema 870-system arranged on various kinds of platforms, stationary, car- and helicopter-mounted. Several factors are of importance in causing surface temperature variations, such as screening from the sun, variation in traffic intensity and construction materials of the road. This article reviews the influence of these factors on road surface temperature and how various platforms could be used to conduct detailed recordings. Sun screening by road rock cuts causes shadow patterns resulting in surface temperatures which are low when compared with sun exposed areas. Height and orientation of the screening object determine the intensity of the surface temperature difference.A maximum surface temperature variation after sunset of approximately 5·0°C was recorded. Road surface temperature differences also occur due to variation in traffic intensity. An intense traffic flow was found to affect the temperature by approximately 1·0°C. Owing to different topographical surroundings and construction, bridges have been shown to differ in temperature when compared with adjoining roads. Variation in road bed material has also been proved to have a great effecton road surface temperature.