[amp_mcq option1=”30″ option2=”20″ option3=”25″ option4=”50″ correct=”option2″]
The correct answer is B. 20 kmph.
The maximum speed of trains during thick & foggy weather in automatic block system is 20 kmph when signal is showing double yellow. This is because the visibility is reduced during thick & foggy weather, and the train driver needs to be able to stop the train in time if there is an obstacle on the track. The double yellow signal indicates that the next signal is at danger, so the train driver needs to slow down and be prepared to stop.
Option A is incorrect because it is the maximum speed of trains during thick & foggy weather in manual block system. Option C is incorrect because it is the maximum speed of trains during normal weather in automatic block system. Option D is incorrect because it is the maximum speed of trains during normal weather in manual block system.