Analyzing the Influence of Traffic on the Urban Heat Island

The Urban Heat Island (UHI) effect, where urban areas are significantly hotter than their surrounding rural areas, has been well documented for more than a century. The major causes are (1) changes to the radiative and thermodynamic properties of the environment and (2) anthropogenic heat generation (Oke, 1982). The built environment in a city generally reduces evapotranspiration and increases the amount of impervious surface compared to the surrounding rural area. In dryland environments, however, this is not necessarily the case - cities may be replacing bare dirt and rock with asphalt and concrete, and the thermal signatures can be very similar (Gluch et al., 2006). In arid environments, then, the influence of anthropogenic heat sources like vehicle and building emissions may be more influential. This study aims to examine the relationship between traffic volumes and the UHI effect in the area of Salt Lake City, Utah. Sites considered have a weather station near or on a roadway and an Automated Traffic Recorder recording the total traffic volume on that roadway. Multiple sites are considered in the area, ranging from urban to rural.

Results show the temperature differences between the roadways and elsewhere are correlated with traffic volumes. Traffic heat emissions account for a sizable portion of the UHI, including in areas on the outskirts of the city that would not normally be included in an UHI study. In the future, further research on this effect in other cities and different climates could make the results more broadly applicable.

Oke, T. R. (1982). The energetic basis of the urban heat island. Quarterly Journal of the Royal Meteorological Society, 108(455), 1-24.

Gluch, R., Quattrochi, D. A., & Luvall, J. C. (2006). A multi-scale approach to urban thermal analysis. Remote Sensing of Environment, 104(2), 123-132. https://doi.org/10.1016/j.rse.2006.01.025