Ride-hailing enjoys global popularity as a door-to-door mobility service, but its pick-up and drop-off inefficiencies and resulting environmental costs are often overlooked. This research examines the potential efficiency and environmental benefits of a flexible pick-up and drop-off (PUDO) strategy, which seeks to improve the routing efficiency by shifting the PUDO locations within short walking distance. A two-stage heuristic method is developed to identify suitable PUDO locations while considering both the detour and congestion factors. Using DiDi Chuxing trip data from central Chengdu, China, we find that 8%–23% of trips can be improved, reducing driving distance and time by up to 15%, and saving 11.6–51.1 GJ of energy consumption and 0.8–3.7 tons of CO${}_2$ emissions in a single working day. Further built environment analysis reveals that areas with one-way and narrow streets, more diverse land use, higher income population, and better public transportation accessibility would benefit more from the proposed strategy. These insights highlight the potential of integrating walking into urban mobility solutions for improved efficiency and environmental sustainability.