## 2 Literature Review  
### Railway Resilience and Railway Accidents Related to Weather  
Rail's resilience refers to the ability of the rail system to cope with technical problems, natural disasters, and social issues and to recover flexibly. This is very important to maintain the reliability, safety, and sustainability of the railway system against various risk situations in railway facilities and operations [3]. The reason is that railways play a pivotal role among transportation infrastructures and have a great impact on economic and social activities, so the suspension or failure of the railway system can cause economic loss, traffic congestion, and social unrest. To prepare for this, railway resilience refers to the ability to continue operation even in unexpected situations and events [4]. Furthermore, rail's resilience is also to prepare emergency response and emergency recovery capabilities so that it can flexibly respond to rapidly changing environments such as rapidly increasing risks and unexpected events and operate safely [5]. In particular, the increase in natural disasters such as heavy rains, floods, typhoons, etc., and the risk of climate change, which we are currently facing globally, are expected to have a great impact on the resilience of the railway system [6]. Accordingly, Rail resilience will be an important factor in determining the safety and sustainability of the system. In accordance with the flow of these changes, many studies have been conducted on global warming, climate change, and natural disasters regarding railway accidents and railway resilience in past studies [7; 8; 9; 10; 11; 12; 13]. However, in previous studies, there is a lack of compressive studies that empirically quantify the risk of railroad accidents linked to detailed weather factors. The reason is that weather can have a significant impact on railroad operations and safety, and there are several ways in which weather can contribute to railroad accidents specifically. For example, heavy rain can cause flooding, which can then damage railroad tracks and bridges as well as destabilize the ground beneath the tracks. This can lead to track failure, derailment, and other accidents [14]. As an example, an Amtrak passenger train was derailed near the town of DuPont, Washington, on 18 December 2017, killing three persons and wounding more than 60 others. The investigation by the National Transportation Safety Board (NTSB) found that the train was traveling at more than twice the posted speed limit at a curve in the track, thus causing it to derail. However, weather also played a role, as heavy rain had caused a landslide to occur, thus damaging the track, and this likely contributed to the accident [15]. Snow and ice can accumulate on tracks and bridges, making it difficult for trains to maintain traction and control. This can cause trains to either derail or collide with other trains or objects [16]. For example, two German high-speed trains crashed head-on near the city of Bad Aibling in Bavaria, Germany, on 9 February 2016, killing 12 people and injuring more than 80 others. The investigation of that crash found that, while signal failure was the primary cause of the accident, weather also played a role: Heavy snow had caused a tree to fall onto the tracks, which had disrupted the signal system and likely contributed to the collision. High winds can push railcars off tracks, especially on elevated tracks or bridges. Wind can also cause trees or other objects to fall onto tracks, thus obstructing train movement [17]. For example, a Union Pacific train carrying coal was derailed near the town of Rock Springs, Wyoming, on 15 March 2018; the accident damaged the track and caused a coal spill, but there were no injuries. The investigation by the NTSB found that high winds likely played a role in the accident by pushing the railcars off the track [18].