Trains may face speed restrictions or limitations when it's too hot due to several factors:
Track Expansion: High temperatures cause metal to expand, including the steel rails on train tracks. When the tracks expand excessively, there is a risk of buckling or warping, which can lead to derailments. To prevent this, speed restrictions may be imposed to reduce stress on the tracks and prevent accidents.
Heat-related Stress on Components: Extreme heat can put additional stress on various components of the train, including the wheels, axles, and bearings. Excessive heat can increase the risk of failures or damage to these components, compromising the safety of the train. Therefore, speed restrictions may be enforced to minimize the strain on the train's mechanical systems.
Power and Overhead Lines: Electric trains rely on overhead lines to supply power. High temperatures can cause overhead lines to expand and sag, potentially leading to contact issues between the train's pantograph (the device that collects power from the overhead lines) and the power supply. To mitigate this, speed restrictions may be implemented to reduce the risk of electrical faults and maintain a consistent power supply.
Heat-related Infrastructure Issues: Extremely hot weather can affect other railway infrastructure elements, such as signaling systems, switches, and crossings. Heat can impact the proper functioning of these components, leading to potential safety hazards or operational disruptions. Speed restrictions help mitigate the risks associated with such infrastructure challenges.
It's important to note that the specific speed restrictions or limitations during hot weather can vary depending on factors like the specific railway network, the type of train, and the local operating conditions. These restrictions are implemented to ensure the safety and reliability of train operations during challenging weather conditions.