Nature-based solution for urban traffic heat mitigation facing carbon neutrality: sustainable design of roadside green belts

Abstract

Urban heat islands (UHI) and heat waves related to climate change can increase urban carbon emissions and endanger human health. Transportation accounts for a large part of UHI and greenhouse gas emissions, which can effectively be mitigated by nature-based solutions (NBS). Roadside green belt is an important element of urban NBS targeting to blck traffic-related pollutants; however, less attention was paid to its impact on mitigating traffic heat emissions. Therefore, the design of roadside green belts was quantitatively investigated considering traffic heat in this work. A new method to rapidly model moving traffic source was proposed, namely urban traffic coupling source (UTCS) method, to deal with the dynamic and complex diffusion of traffic-generated heat. The impact of roadside green belts' locations and types on the thermal environment of cities' motorized and non-motorized area was investigated. The design parameters (tree spacing and shrub length) were evaluated for the optimum co-benefits between cooling efficiency and nurture management costs. Results showed that placing trees and shrubs near non-motorized lanes and sidewalks provided a favorable cooling effect, with the non-motorized areas' temperature decreased by up to 1.05 °C. When the range of tree spacing and shrub length were 0–0.375 W and 0.17–0.63 L (W and L are the width and length of the road, respectively), a maximum co-benefit improvement of 45.7% could be achieved. Moreover, this work provides a guideline for sustainable design of roadside green belts to improve the urban climate and achieve carbon neutrality target.