Study of the thermal environment of sidewalks within varied urban road structures

Abstract

Vehicle-oriented transportation has been dominating road design for decades and worsening the urban outdoor thermal environment. Introducing the concept of human-oriented design in road reconstruction, this study considered road orientation, number of planting strips, and leaf area index (LAI) of trees when developing alternative road structures that aims to provide pedestrians a more satisfying walking experience. The ENVI-met V4 model, was used to simulate the thermal environment of sidewalks within the scenarios. Results demonstrated that road orientation had significant but time-varied effects on mean radiant temperature (Tmrt) and physiological equivalent temperature (PET). Two Tmrt and PET peaks were noticed in East-West (EW) oriented roads; but only one peak was found in North-South (NS) roads due to that the aisle buildings on NS roads shaded sidewalks and reduced the solar radiation received in the morning.Changing tree’s LAI from low to high on EW and NS roads can reduce the mean Tmrt by 5.5 and 3.0 °C, and the mean PET by 3.2 and 1.7 °C, respectively. Simulation results also showed that adding one more planting strip in the middle of roads did not reduce the mean Tmrt (all cases less than 1.7 °C) and mean PET (all cases less than 1.2 °C) much. A significant synergistic cooling effect from road orientation, number of planting strips, and LAI of trees on the sidewalks’ Tmrt and PET was observed. Thus, the number of planting strips and LAI of trees could be more precisely applied while considering road orientation. These results provide quantitative and alternative information for designers to create a better walking experience for pedestrians.