The effect of screening on road surface temperatures is analysed using data
from the Swedish road weather information system (RWIS) together with data
from thermal mapping. The study deals with the analysis of temperature
variations caused by shading of the road surface during clear daytime
conditions and focuses on the relation between solar elevation and magnitude
of road surface temperature differences between screened and sun-exposed
areas. Also included is an analysis of how the temperature differences
during the day affect the establishment of temperature variations after
sunset and the time it takes after sunset for temperature differences caused
by shading to decline. The results show that the magnitude of road surface
temperature differences between sun exposed and screened sites
(RSTdiff) that develop during clear day conditions can
be attributed to solar elevation (β) and can be expressed by the
equation: RSTdiff=−2.7+0.46(β). A
relationship between the daily maximum temperature difference andthe
preservation of the screening effect after sunset is observed. The effect
after sunset can be described by:
RSTdiff=A−Bh+Ch2−Dh3−Eh4+Fh5,
where h is the time in hours after sunset and A to F
are constants related to the time of the year at the actual site.