At least 25 people died and 50 were injured when two trains derailed within minutes of each other while crossing a small bridge in Madhya Pradesh, shortly before midnight on Tuesday. The Kamayani Express, going to Varanasi in Uttar Pradesh from Mumbai, derailed near Harda town, 160 km south of Bhopal. The Janata Express, en route to Mumbai from Patna, too derailed at the same spot minutes later.
Derailment is not very common. Last year less than 1 per cent of train accidents were due to derailments and mere 0.23 per cent of death on tracks occurred due to it.
What causes tracks to dislocate?
Usually derailment caused by flash floods happens in deserts where ecology cannot handle large quantity of water.
Rail tracks can give way because sand is not a strong binder.
But the possibility of such derailment is very low, in places like Madhya Pradesh, where the soil has clay which supports tracks.
If the temperature differential in a day is very high then the current long-welded rails can fracture, theoretically. This possibility is particularly high in March or November months but it is not common. Welding flaw, obstruction on track or landslide can be other reasons.
What does Railway do in rains?
According to a former official in the Indian Railways' mechanical wing, there is an institutionalised arrangement whenever there is a weather prediction for heavy rains.
Monsoon patrolling of tracks is carried out by the gangman. Besides, drivers are cautioned.
"Overspeeding cannot cause derailments since tracks are tested with rolling stock running at 10 per cent higher speed than normal. Besides, unlike road, rear wheels of trains are guided by track and not speed so they usually do not jump off the track."
How can defects be detected through automatic systems?
Track circuiting can detect defects early without manual patrolling. It is, however, possible to implement this only on small stretches like suburban systems because of high cost.
