Development of bus prior perimeter strategy in bi-modal urban networks

Perimeter control has been proposed as a promising method to alleviate traffic congestion in core areas. Despite its rapid development, a possible limitation of classical perimeter control is that it ignores bus priority in dual-mode networks. To address this issue, this article developed a Bus Priority Perimeter Control (BPPC) strategy that combines flexible-sharing bus zones with gradual speed limits upstream of perimeter intersections. Microscopic simulation shows that compared with traditional perimeter control, BPPC can enhance bus priority passage. Under the baseline scenario (5-minute bus headway), the standard deviation of headways decreased from 3.32 to 1.90, with the average travel time per kilometer traveled (TTKT) reduced by 8.71% in the core and by 15.14% in the peripheral. Meanwhile, compared with the flexible-sharing dedicated bus lane strategy, BPPC also improved the flow of private cars, reducing the average car TTKT by 7.25% (core) and 13.21% (peripheral), while continuously reducing the variability of travel time. When the bus headway is shortened to 3 min or extended to 10 min, these advantages remain. Overall, BPPC achieves a more ideal balance between bus priority and overall traffic efficiency, while maintaining or even improving the flow of private cars and enhancing the reliability of bus services.