What is the main reason for prohibiting water use on fires near the third rail?

Using water to extinguish fires near the third rail is prohibited mainly due to the significant shock hazard it poses. The third rail is a crucial part of the train's electrical system, supplying power to the trains. When water is applied in this environment, it can conduct electricity, increasing the risk of electric shock not only to firefighters but also to any bystanders in the vicinity. Electricity from the third rail can create a dangerous situation where live wires are exposed to water, leading to a potentially fatal scenario. Therefore, fire suppression techniques that do not involve conductive materials, such as water, are essential to ensure safety in such situations.

The other options discuss various effects of water use in firefighting but do not address the immediate safety risk posed by the combination of water and live electrical components.