Environmental Impact from Vehicle–Pedestrian Interactions at Unsignalized Mid-Block Raised Crosswalks: A Microscopic Perspective

Unsignalized mid-block raised crosswalks are widely used to improve pedestrian safety by prompting drivers to yield. However, on arterial roads they conflict with vehicular continuity, while their environmental effects remain insufficiently understood. This study uses field-informed microscopic simulations to examine these effects across the full range of pedestrian and vehicle influx. The raised crosswalk reduces the maximum traffic current by 42.6%, causing the system to exhibit three phases: quasi-free flow, jamming, and blocking. Quasi-free flow was the most relevant because it combined high throughput with frequent deceleration and re-acceleration under conditions observed during most of the operating day. In this phase, the mean instantaneous CO2 emission rate increased by 23.08%, revealing a spatial asymmetry: emissions decreased by 35.66% upstream but increased by 51.87% downstream. NOx and PMx showed similar downstream patterns, whereas CO reflected upstream stop-and-go dynamics. Exploring a solution to this operational incompatibility, this study evaluated a zebra crossing controlled by a pedestrian-actuated signal. By coordinating pedestrian and vehicular right-of-way, this configuration reduced mean CO2, CO, NOx, and PMx emission rates by 18.3%, 40.61%, 26.75%, and 38.96%, respectively. Overall, these findings highlight emissions as a critical evaluation criterion and provide decision-makers with evidence-based insights for assessing pedestrian infrastructure.