A man carries his wife on his back as they make their way with their luggage along a flooded tunnel to catch their train, after heavy rainfall hit Jinhua, Zhejiang province, China, July 21, 2015. (Photo by Reuters/China Daily)

In this photo taken on Thursday, July 23, 2015 migrants enter a train to Serbia at the railway station in the southern Macedonian town of Gevgelija. The country has become a major transit route for thousands of Middle Eastern and African refugees and migrants who cross over from Greece and then continue into Serbia. (Photo by Boris Grdanoski/AP Photo)

New York City policemen tangled with demonstrators at a subway station on the opening day of the New York World's Fair, April 22, 1964. Youths attempted to stall the train, which was headed from the city to the fairgrounds, as a form of protest on behalf of civil rights for blacks. (Photo by Charles Gorry/AP Photo)

Migrants ride on top of a northern bound train toward the US-Mexico border in Juchitan, southern Mexico, Monday, April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. (Photo by Eduardo Verdugo/AP Photo)

Passengers climb to board an overcrowded train at a railway station in Dhaka August 8, 2013. Millions of residents in Dhaka are travelling home from the capital city to celebrate the Muslim Eid al-Fitr holiday, which marks the end of the Muslim holy fasting month of Ramadan. (Photo by Andrew Biraj/Reuters)

Culinary Specialist 2nd Class Jaqueline Rodriguez subdues a simulated suspect after being sprayed with oleoresin capsicum (OC) spray during security training aboard the amphibious dock landing ship USS Comstock (LSD 45). (U.S. Navy photo by Mass Communication Specialist 2nd Class Joseph M. Buliavac/Released). May 10, 2011

July 23, 2013 – Kampala, Uganda. Helene and Diana train daily more than 2.5 hours by Innocent Kapalata, a passionate and ambitious former boxer. Amidst the shanty homes a group of ambitious fighters are trying to reach for a better life. (Photo by Peter Bauza/ZUMA Press/VISUAL Press)

People try to board an overcrowded passenger train as they travel home to celebrate Eid al-Fitr festival, which marks the end of the Muslim holy fasting month of Ramadan, at a railway station in Dhaka, Bangladesh, July 5, 2016. (Photo by Adnan Abidi/Reuters)