Ever since the midterm elections, there’s been quite a bit of buzz about the possibility of a Green New Deal, a comprehensive national plan to tackle climate change and inequality all in one. On February 7, Rep. Alexandria Ocasio-Cortez (D-NY) and Sen. Ed Markey (D-MA) finally unveiled a resolution on Capitol Hill. Rather than a set of distinct policies, it’s more of a set of goalposts with ambitions for fighting climate change and transitioning the economy in a just way.

Because it’s so vague in its particulars, the resolution has become something of a Rorschach test as observers try to figure out how a Green New Deal would materialize in the real world. Some clues emerged in what looked like a hastily assembled FAQ on Ocasio-Cortez’s website that’s since been taken down.

Specifically, the section of the FAQ on transportation calls to “build out high-speed rail at a scale where air travel stops becoming necessary.” The resolution itself doesn’t mention air travel at all but does call for the goal of “investing in ... clean, affordable, and accessible transportation; and high-speed rail” as part of a 10-year national mobilization.

Still, the air travel line drew some attention, particularly among conservatives:

Fox & Friends has a full-on freakout about the Green New Deal, because .@AOC "wants to change the way you heat your home, the way you cook your food, replacing air travel with trains, unionize all jobs, and guarantee income for all" pic.twitter.com/24DEg47Ytu — Bobby Lewis (@revrrlewis) February 8, 2019

For a big, ambitious plan to fight climate change, it would make perfect sense to target transit in general and air travel in particular. Transportation — planes, cars, shipping — is the largest source of greenhouse gas emissions in the United States. Surging air travel demand helped fuel the rise in US emissions after years of decline. And aircraft are extremely difficult to decarbonize. While electrification is coming for cars, trucks, and buses, no battery or fuel cell is going to fly anyone across the Pacific anytime soon.

So alternatives to flying tend stand to be better for the environment. The International Energy Association noted this month in its Future of Rail report that trains carry 8 percent of the world’s motorized passengers and 7 percent of freight, yet use just 2 percent of the energy consumed in the transportation sector. That means trains are a very energy-efficient way to get around.

But could high-speed rail really replace a significant amount of air travel? Actually, yes, depending on the distance.

Trains already compete with planes in many parts of the world

Certainly, no one is going to lay rail across the ocean, but in many countries, we’re already seeing high-speed trains go toe to toe with planes between major cities. The United States does have a what can technically be called a high-speed train, Amtrak’s Acela Express. But it only runs between Washington, DC, and Boston and averages 68 mph with a top speed of 150 mph, which is pretty meager compared to the high-speed train offerings in a handful of other countries. China, Spain, Germany, Saudi Arabia, France, Italy, South Korea, and Japan all have trains that top out above 200 mph.

Bloomberg last year put together an excellent analysis of busy transit routes in Europe, North America, and Asia, comparing flights and train trips in terms of time and cost. When factoring in the time it takes to get to the airport, wait in security lines, and travel from the airport to the destination, high-speed trains are roughly on par. We see this in trips between city pairs like Beijing and Shanghai, London and Brussels, and New York and DC.

One of the proposals in the “Green New Deal” is to build high-speed train lines so flying is less necessary. This is not a radical proposal. In Japan, the Shinkansen covers distance approx LA-San Francisco in 2.5 hrs. At peak, trains every 10 minutes. The line was built in 1964. — Katie Mack (@AstroKatie) February 8, 2019

Also, the Beijing—Shanghai route carries about 180 million riders a year, about as many as rode on all of Delta Airlines' network in 2017, — Yonah Freemark (@yfreemark) December 21, 2018

“Travel time is most critical in determining the competitiveness between the [high-speed rail] and air transport: shorter travel time will attract more passengers,” according to a 2017 review study in the Journal of Advanced Transportation.

The prices are comparable too, with train tickets actually coming in cheaper for routes like Paris and Lyon or Seoul and Busan. The Paris-Lyon train fare is about $75, while the flight is about $115. Both trips take about 2.5 hours door to door.

The paper also notes that aircraft start beating bullet trains in costs and travel times over distances greater than 620 miles. That’s just a bit more than the distance between Los Angeles and Salt Lake City. So even with a high-speed rail network across the US, there will still be a market for air travel, and no one is proposing to get rid of airlines. It’s just that high-speed trains can replace many short-haul flights, giving travelers more options if they don’t want to fly.

“It’s perfectly reasonable to think we can have air travel, high-speed rail, and highways,” said Yonah Freemark, a doctoral candidate studying the politics of transportation at MIT. And adding more options like high-speed trains makes it easier for travelers if they don’t want to fly.

Shifting from aircraft to trains drastically reduces greenhouse gas emissions

Are high-speed trains good for fighting climate change? In general, yes, but there are some caveats. Like electric cars, high-speed trains run on electricity, which is only as clean the generators that produce it. Running electric trains on coal power still has a carbon footprint.

Nonetheless, taking a train is still far, far less carbon-intensive than flying. A 2018 study in the Journal of Advanced Transportation looking at transit in Europe reported “a remarkable advantage of high speed trains compared to aircraft, with regard to direct [CO2-equivalent] emissions per [passenger-kilometer].”

Another factor to consider is that building a rapid transit network will also induce its own demand, to an extent, so it won’t siphon off air travelers alone. On the other hand, trains also compete with cars and buses, so the passengers they take off highways is another added environmental benefit.

Could the United States ever pull off a respectable high-speed rail system? “Outside of the US, Canada, and Australia, every developed country has invested quite considerably in high-speed rail transportation systems,” Freemark said. “I think there is no reason to think that the United States is any different [in its transportation potential] than any other country.”

Before you say, “The US is big!” consider that China, another vast country, is building out a massive high-speed rail network, not just within its borders but throughout Southeast Asia. It already has the largest high-speed rail network in the world, with more than 15,500 miles of track, and aims to double it by 2030.

Freemark said it’s helpful to think of rail in the US across several transit corridors — New England, California, Texas, Florida, the Midwest — rather than as a singular network. Pared down, the economics and logistics of high-speed rail start to become more feasible. There are already some efforts underway, like Brightline in Florida. However, building up these networks such that they can compete with air travel will still require more investment.

California has already found this out the hard way. Gov. Gavin Newsom announced this week that California is dialing back its high-speed rail project, originally meant to connect Los Angeles and San Francisco, because of an estimated cost of $77 billion.

“I have nothing but respect for Governor Brown’s and Governor Schwarzenegger’s vision. I share it,” Newsom said in his State of the State address. “But let’s be real. The current project, as planned, would cost too much and take too long.”

The new scope of the project will connect the cities of Merced and Bakersfield.

And indeed, building a new national high-speed rail system to compete with air travel would be expensive. But it has to be compared to the costs of our existing system of highways and airports, according to Freemark. Our existing transportation infrastructure requires ongoing maintenance and will require billions of dollars’ worth of upgrades to cope with rising demand. “No matter what, with a growing population, we’re going to be investing in a high-speed transportation system,” Freemark said. Whether it’s trains or more aircraft is up to us.

Choo-choo!