Most American passenger trains, including Amtrak’s popular Acela service, run at speeds that are far slower than the superfast European and Japanese trains that can zip along at 200 miles per hour or more. The main reason is that, despite modest investments, American lawmakers have not given high-speed rail the priority it deserves.

High-speed rail can play an important role in the nation’s transportation system by reducing congestion at airports and on highways. It can also provide a big economic boost while helping to reduce pollution that is causing climate change. That is why President Obama gave it an important place in the 2009 stimulus bill, which helped kick-start projects to upgrade rail lines and build new ones around the country.

Since then, the federal government has spent about $11 billion on high-speed rail, with only a few visible improvements in American passenger rail service, as a recent Times article pointed out. That should not come as a surprise. Bringing high-speed rail service to the United States was always going to take time and money. In 2012, Amtrak estimated that updating rail lines and trains between Boston and Washington to speeds of 220 m.p.h., up from the Acela’s average speed of about 84 m.p.h., would cost $151 billion. Even getting the Acela to travel at 160 m.p.h. for longer stretches will require laying new track, building new tunnels and replacing signals.

Amtrak is already doing some of that, but more federal support is needed. California’s plan to link Los Angeles to San Francisco by high-speed rail is expected to cost $68 billion. Critics argue that such services cannot survive without public subsidies and that the United States has few of the dense urban areas that have made such train services successful in places like France and Japan. But these arguments fail to acknowledge that most forms of public transportation are subsidized somehow by the government; the federal government puts up most of the money to build the interstate highway system. Skeptics also greatly underestimate the country’s long-term transportation needs. The Census Bureau estimates that the American population will cross 400 million in 2051, and the country is becoming more urban, not less. California’s population is predicted to top 50 million in 2049. That growth will put an incredible strain on the nation’s highways and air-traffic system.