With the increase of low-cost, short-haul airline flights beginning in the 1950s, air traffic is becoming a significant source of CO2 emissions. A study conducted by French researchers found planes emit 77 times more CO2 per passenger than trains for journeys lasting under four hours. But there is a shift towards rail travel. After the pandemic, 47% of U.K. travelers reported that they wish for a slower pace of life that was more appreciative of nature. "Many are finding that you don't have to suffer to save the planet — it's pleasurable to take the train," says Mark Smith, who is also known as the Man in Seat 61. Low-carbon train companies such as Lumo are focusing on affordable travel, with some 60% of train fares costing £30 ($40) or less. Others are even re-popularizing sleeper services, such as Nightjet and Snälltåget. The hope is to shift Europe's dependency from airline travel to rail travel.