Mitigating urban heat along roadways; systematic review of impact and practicability

Roads contribute to the urban heat of cities. Their design, landscaping, morphology, and materials influence the microclimate and accumulation of heat at local to boundary scales. Roadways contribute up to 35 % of the urban landscape yet remain a relatively under research area within the UHI literature. This paper presents a systematic review of 248 articles exploring the extent to which roads can mitigate Urban Linear Heat (UHI_ULI). As roads differ in their design and function, the analysis of the research has applied a three-tier road hierarchy based on approximate number of lanes (state, regional and local) and assessed the practicability of urban heat adaptation measures. The analysis reveals that the microclimate of roads can successfully modify through enhancing the level of tree canopy cover and through implementing water-sensitive urban design (WSUD) features. Benefits are greater along local roads being narrower, although strategies such as median strip vegetation plantings can have significant cooling benefits for wider regional and state roads. This review can inform the design and adaptive management of roadways to ameliorate the impact of a warming climate and urban heat.