Previous investigations of the Urban Heat Island (UHI) effects have highlighted the long-term negative impacts of urban street canyons on surroundings temperatures that indirectly contribute to global warming. Studies on road pavement solar collector (RPSC) system have shown the potential of reducing the heat' rom the pavement surface by absorbing the heat from the pavement and harnessing the thermal energy. This study expands the investigation of optimising the RPSC system based on four tested parameters (pipe diameter, pipe depth, water velocity and water temperature) comparing the system performance in terms of Delta T of inlet-outlet, potential thermal collection (PTC) and surface temperature reduction (STR). Two types of external environmental conditions were considered: (i) urban domain resembling a street canyon (ii) flat surface resembling a low density or rural area. 'De-coupled' CFD method was employed based on previously author's published work by simulating the effect of external environment (macro domain) onto RPSC system (micro domain) in two separate CFD modelling. Initially, both domains were validated with numerical and experimental data from previously published works. In comparing the RPSC application in urban domain and flat/rural domain; it was found that the system adjustment based on high and low conditions of water velocity provided the best performance improvement with average 28% higher in terms of PTC and STR as compared to other simulated parameters. Yet, insignificant Delta T (less than 5 K) was obtained with values over 0.02 m in the pipe diameter and in the 0.25 m/s water velocity. (C) 2016 Elsevier Ltd. All rights reserved.