In 2015, 910 million Chinese traveled by all forms of rail—more than twice the 415.4 million who flew, according to the journal article. Unsurprisingly, the future of train technology resides in China. The first magnetic-levitation, or maglev train, which can travel as fast as 267 mph (430 kph), operates in Shanghai; engineers are researching future maglev trains that could travel at a stunning 373 mph (600 kph), an achievement that could thoroughly upend the current dynamic between air and ground travel.

Over time, Chinese airlines and high-speed trains have generally evolved so that fares and service classes are comparable, said Yu Zhang, an assistant professor of civil and environmental engineering at the University of South Florida and one of the journal report’s authors. In their early days, Chinese high-speed rail operators sought to emulate airlines in terms of attendant training, with fares that were generally too high to spur much demand, she said. Since then, train fares have dropped.

“Air service is impacted, but we do not see a significant reduction of passengers, either,” Yu said of the Chinese market. “It’s really dependent on the particular route.”

In Europe, the Eurostar high-speed rail from London to Paris and Brussels served 10 million riders last year, the fourth since it first topped that mark. The service began in November 1994 and drew 2.9 million passengers the following year. Current Eurostar fares begin at 29 pounds ($39), down from initial fares of 79 pounds in the system’s early days.

Again, the different modes of transport that might seem to be rivals for the same passengers are in many way complementary. Low-cost airlines focused on short-haul routes and European high-speed rail options that would seem to compete are generally not rivals, given their vast differences on other counts. The trains generally serve city centers, while the air carriers tend to use secondary airports further afield as a way to lower their costs.

On the Paris-Bordeaux line, high speed rail is “by far the most competitive travel offer with a real traffic growth of 70 percent since its launch in July,” the French railway SNCF said in an emailed statement. “In November, we reached 82 percent of the Paris-Bordeaux travel market share,” SNCF official Rachel Picard said. “This high speed benefits all customers, including professional travelers whose number has doubled compared to 2016.”

And what happened to the big airlines on the continent such as Air France-KLM? They have ceded traffic on the shorter routes to low-cost rivals, including Ryanair Holdings Plc and EasyJet Plc. Many major U.S. airlines are following suit, abandoning smaller regional jets and reducing service to less-populated cities.

“The way airlines think of trips that are short-haul has changed,” said Holly Reed, an executive with Texas Central Partners LLC, which is raising money to build a bullet train between Dallas and Houston.

By now, you may have noticed the absence of one large country from this discussion. After a century of neglect, U.S. transit infrastructure has more in common with the developing world than with China or Western Europe. While Asia rail systems measure their passengers in the hundreds of millions, in the U.S., Amtrak had 31.3 million riders in its 2016 fiscal year.

America’s fastest train, the Acela, travels on the Boston-New York-Washington corridor with a speed capability of only 150 mph (241 kph)—but the trains rarely exceed 100 mph (161 kph) due to congestion—and then only for short periods on aging tracks. With the rails often running parallel with the busy Interstate 95, it’s not uncommon to see cars outpacing locomotives.