A simulated casualty is evacuated during an emergency services exercise at the disused Aldwych underground station on February 22, 2012 in London, England. Operation Forward Defensive aims to test the response to a terrorist incident on the London Underground network during the 2012 Olympic Games. (Photo by Peter Macdiarmid/Getty Images)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

Policewomen take a picture inside a tunnel under the Chao Phraya river at a Mass Rapid Transit subway station in Bangkok, Thailand, December 14, 2015. (Photo by Athit Perawongmetha/Reuters)

A migrant carries his belongings as he arrives at the Beijing railway station to catch a train in Beijing, Friday, February 13, 2015. (Photo by Andy Wong/AP Photo)

A Swiss police officer accompanies a migrant from Syria carrying her baby, upon her arrival at the railway station in the north-eastern Swiss town of Buchs September 1, 2015. (Photo by Arnd Wiegmann/Reuters)

Mongolian President Tsakhiagiin Elbegdorj (C) walks towards the media after casting his vote for the parliamentary elections at a polling station in Ulaanbaatar, Mongolia, June 29, 2016. (Photo by Jason Lee/Reuters)

A girl carries utensils after filling them with water from a pipe that supplies water to trains at a railway station on the outskirts of Agartala, India, February 28, 2017. (Photo by Jayanta Dey/Reuters)

A woman chops a fish at her stall as a train passes by at a morning market near Duri train station in Jakarta in this February 12, 2009 file photo. (Photo by Reuters/Beawiharta)