Green Bay Packers' Johnathan Calvin rides a bike to NFL football training camp on July 27, 2017, in Green Bay, Wis. (Photo by Morry Gash/AP Photo)

Two holidaymakers amuse themselves with a porter's trolley whilst waiting for their train at Euston Station, London, 5th August 1939. (Photo by A. J. O'Brien/Fox Photos/Getty Images)

Heimana Reynolds of USA in action during a training session prior to the World Skate Park World Championships at the Parque Candido Portin​ari in Sao Paulo, Brazil, 11 September 2019. (Photo by Sebastião Moreira/EPA/EFE)

A couple shares a light moment in a Mass Transit Railway (MTR) subway train in Hong Kong, China on August 28, 2019. (Photo by Anushree Fadnavis/Reuters)

A woman sits next to a Gollum figure on the “Middle-earth Shuttle” subway train November 18, 2003 in New York City. The train's cars were decorated with Middle-earth creatures, vines, moss and stones to celebrate the November 18 DVD and VHS release of the Special Extended Edition of The Lord of the Rings: The Two Towers. (Photo by Mario Tama/Getty Images)

Men look out from a carriage train as it leaves from the Nizamuddin Railway Station on February 06, 2012 in New Delhi, India. The Nizamuddin Railway Station serves as the main station connecting all major cities, and is served by Northern Railways. (Photo by Daniel Berehulak/Getty Images)

Ford displays the drive train of the F150 Raptor SVT truck during the media preview of the Chicago Auto Show at McCormick Place on February 8, 2012 in Chicago, Illinois. The show, which is the largest and oldest auto show in the country, opens to the public on February 10. (Photo by Scott Olson/Getty Images)

An instructor (C) adjusts the posture of students of flight attendant major during a training session at Anhui Foreign Languages University, in Hefei, Anhui province, China, May 25, 2015. (Photo by Reuters/China Daily)