Unplanned rail disruptions result in substantial delays to passengers and severe effects on the economy of a large city like Toronto. While bus bridging has been a widely adopted method to replace the subway service in such events, its effect on the operational resilience of the subway service is less often studied. This study assesses the resilience of the subway network of Toronto employing an optimal bus bridging strategy. First, subway incidents are categorized based on their characteristics using K-mean clustering analysis. The incidents are then grouped based on the performance of optimal bus bridging plans. Classification and regression tree analysis is used for this task, employing two metrics: the total user delay and total number of shuttle buses under the optimal bridging scenario. Queueing and optimization models developed previously by the University of Toronto are used to determine and simulate the optimal bus bridging plans of a sample of incidents. The severity of unplanned disruptions is finally demonstrated using a severity scale and the effect of incident duration uncertainty is analyzed. The results show that along the congested city alignments, where the capacity of the roads and stations is limited, the bus bridging service is often insufficient to replace the train service. However, it could be a good alternative in uncongested subway segments where the available street capacity is relatively high, allowing large bus volumes to serve the corridor. This model is easily applicable to different rail systems and it could assess other systems to produce better bridging plans.

计划外的铁路中断会导致乘客大量延误，并对像多伦多这样的大城市的经济造成严重影响。尽管在这种情况下，公交桥接已被广泛采用以代替地铁服务，但很少研究这种方法对地铁服务的运营弹性的影响。本研究采用最佳公交桥策略评估了多伦多地铁网络的弹性。首先，使用K均值聚类分析根据地铁事件的特征对其进行分类。然后根据最佳总线桥接计划的性能对事件进行分组。分类和回归树分析用于此任务，采用两个指标：最佳桥接情况下的总用户延迟和穿梭巴士的总数。多伦多大学先前开发的排队和优化模型用于确定和模拟事件样本的最佳总线桥接计划。最后，使用严重性量表证明了计划外中断的严重性，并分析了事件持续时间不确定性的影响。结果表明，在拥挤的城市路线上，由于道路和车站的容量有限，公交桥接服务通常不足以代替火车服务。但是，这可能是不拥挤的地铁路段的不错选择，在这些路段，可用的街道容量相对较高，允许大量的公交车驶入走廊。该模型很容易适用于不同的铁路系统，并且可以评估其他系统以产生更好的桥接计划。