应对突发大规模流行病的城市常规公交管控策略

公共交通内部相对狭小和密闭的空间，使得乘客间频繁发生近距离接触，是流行病扩散的高危环境。面对诸如新型冠状病毒肺炎这类突发大规模流行病时，交通管理者通常采取的方案是全部公交线路停运，彻底阻断流行病通过公共交通系统传播这一个途径，但是对于公交乘客而言，如果缺乏替代的出行方式，将严重降低其移动性，甚至会影响其基本的生活条件。利用北京市公交IC卡刷卡数据，挖掘乘客的个人出行特征和相互之间的接触特征，构建公交乘客动态接触网络，试验数据统计显示北京公交乘客单次出行与他人的平均接触时间为17 min，通勤乘客工作日与他人平均累计接触123次。利用理论传播模型（SEI和SIS）模拟流行病在公共交通系统内的扩散，对比随机网络分析其特征，发现公交乘客间接触的周期性发生规律显著促进了流行病的快速传播。将乘客传播影响力集计至公交线路，针对常规公交网络设计停运部分线路的运营方案，使用站点间平均邻接距离作为指标，衡量部分停运方案导致的常规公交系统可达性损失。研究对比了停运方案实施前后的流行病扩散规模。研究结果表明，只需要停运小部分线路就能使流行病暴发得到遏制，同时公交系统的整体可达性没有明显下降。

Control Strategy for Urban Public Transit in Response to Large-scale Emergent Epidemic

The relatively small and confined space inside public transportation vehicles, which induces frequent and close contact between passengers, is a high-risk environment for the propagation of infectious disease. In the face of a sudden, large-scale epidemic such as the COVID-19, the strategy usually adopted by traffic managers is to shut down all bus lines, thus completely blocking disease transmission through the public transport system. However, for bus passengers, the lack of alternative means of public transport seriously reduces their mobility and even affects their basic living conditions. Here, we have explored the characteristics of individual passenger travel and contact among passengers, and have reconstructed dynamic contact networks based on data from bus IC cards in the city of Beijing. Experimental data show that the average contact time between any pair of bus passengers on a single trip is 17 min, and the average cumulative contact times between one commuter and other passengers during weekdays is 123 We used the Susceptible-Exposed-Infected (SEI) and Susceptible-Infected-Susceptible (SIS) models to simulate the dynamics of disease spread on such temporal networks, which led to the discovery of an efficient control strategy. Compared with a simulation on random networks, we found that the periodic occurrence of contact between bus passengers significantly promoted the rapid spread of disease. For conventional bus networks, we designed a partial shutdown scheme by aggregating the individual transmission influence into the bus lines, and used the average transfer distance between bus stations as an indicator of the reduced accessibility of the conventional bus system due to partial shutdown. The scale of the epidemic before and after the implementation of the partial shutdown scheme were compared. We found that disease outbreaks could be contained by stopping a small number of bus lines, and that the overall accessibility of the bus transportation system did not decrease significantly.