Melissa Schleig, a postmaster who lives in Strasburg, Virginia, drove more than 400 miles southwest to the Smoky Mountains to see the 2017 solar eclipse. The travel experience was miserable.

“It should have taken us about six to seven hours to go down there but it took us about a little over six hours just to go about two hours south of here. It was insane,” said Schleig, who began to drive down the day before the eclipse. 

At least 5 million people traveled for the 2017 eclipse, according to a journal by the Institute of Transportation Engineers, but even more are expected to gather to witness this year’s total solar eclipse on April 8. Already, an estimated 31.6 million people currently live in the roughly 115-mile wide path of totality—compared to the 12 million that did in 2017. 

“Having a total solar eclipse pass through the U.S. is kind of like having 20 or 30 Super Bowls happening all at once,” says Richard Fienberg, project manager of the American Astronomical Society’s Solar Eclipse Task Force. “So many people are gathering for the spectacle over a long distance.”

Read More: How Cities Around the U.S. Are Celebrating the Eclipse

Transportation agencies are coordinating with the National Weather Service to spot areas of high interest for eclipse viewing to better prepare for traffic delays, but they say the impacts are unavoidable. “The Federal Highway Administration (FHWA) knows that there is great interest in this rare solar event, and that’s why we want everyone to be aware of the real traffic and safety impacts,” FHWA Administrator Shailen Bhatt told TIME in an email. “We want people to remember this day and this experience—that may be once in a lifetime—for all the right reasons.”

This year Schleig, who is part of a Facebook eclipse chasing group, is traveling to the Canadian side of Niagara Falls to view the eclipse. And she’s hoping to learn from her 2017 mistakes: she’s planning to avoid the traffic by extending her trip from April 4 through the 10th, instead of driving the day before like she did last time.

How bad will traffic be? 

The FHWA says Schleig has the right idea. It is advising people to drive early, and stay longer in the town where they’re viewing the eclipse to avoid traffic. The FHWA says it’s hard to predict which cities or states will be most impacted by the eclipse traffic-wise, but they predict up to 5 million people will be traveling to the path of totality between Texas and Maine.   

While drivers and officials are looking to the 2017 eclipse for hints of what is to come, traffic will likely be much worse this time. That’s because the 2024 path of totality—the area where the moon will completely obscure the sun—is a 3-hour drive away from 8 major cities with a population greater than 2 million, including Chicago, Houston, and Toronto. By contrast, the 2017 eclipse path of totality was a 3-hour drive away from only three larger metropolitan areas: St. Louis, Kansas City, and Portland, Ore.

Read More: How to Use Your Smartphone to Take Photos of the Solar Eclipse

If the expected 5 million visitors were to leave the path of totality as soon as the eclipse ends, the ensuing traffic would be equivalent to 71 sold out football games ending all at once, according to a journal by the Institute of Transportation Engineers.

Where are people traveling?

Several eclipse chasers, like 62-year-old photographer Beth Hutter, told TIME that they were planning to travel to Texas because it has the lowest chance of cloud cover. “We didn’t want to take a chance that the day of the eclipse it [would be] overcast and rainy,” said Hutter, who is traveling from Michigan to Kileen, Texas five days before the eclipse. “We made the mistake of trying to drive home the same day [for the 2017 eclipse]… So thankfully, because we’re going to be right there, I don’t think we’re going to have to deal with the traffic nightmares that most people are going to have.”

Texas Department of Transportation media relations director Adam Hammons says that up to one million out-of-state visitors may be traveling to view the eclipse, in addition to the millions that already live in the state and will likely also be driving to different areas/cities.  

Hammons says the eclipse runs through I-35, which is a significant corridor in the state that traverses through small towns as well as larger metro areas like Austin, Dallas, and Fort Worth. “It really goes through a large portion of Texas,” he says. “There’s going to be some possible significant delays on these major corridors and/or farm roads…Give yourself extra travel time. Plan ahead your trip, plan your route,” Drivetexas.org, a website that shares real-time traffic updates, could be helpful in deciding which way to go. 

Regardless of where you choose to see the eclipse, Hammons says it’s important to have a safe, designated place to park and enjoy the experience—as long as it’s off the shoulder of the highway.

Read More: Here’s What Determines How Long the Total Eclipse Will Last in Your Location

Other states like Arkansas, which has a population of some 3 million people, could see anywhere from 300,000 to 1.5 million visitors. (State officials have cited varying estimates.) The most extreme traffic will be seen along AR Highway 70 to Benton, AR Highway 65 from Conway to Greenbrier, and more. “There’s no doubt our Interstates and highways could be tested,” Arkansas Department of Transportation Director Lorie H. Tudor told TIME in a statement, “but we have put forth our best planning efforts and we are cautiously optimistic that we are as prepared as possible to address any foreseeable issues that may arise.”

New York is another state expecting a high volume of visitors and traffic. Many residents and out-of-state visitors will be traveling to the western and northern regions of the state, with Niagara Falls being an area of high interest. “We are expecting as many as a million people to come to Erie County solely for the eclipse,” says Peter Anderson, press secretary for the Erie County executive, where Niagara Falls is based. According to data collected by Priceline and shared with TIME, Buffalo, New York has the second highest average airfare price compared to the travel cost to seven cities along the path of totality— including Dallas, Indianapolis, and Cleveland—at $999, and the most expensive average nightly hotel room cost among those cities listed at $476.

Still, for many of the eclipse watchers, braving bad traffic will be worth it. “It’s just one of those things where you just realize your place in the world, and how small you are in comparison to the rest of the universe,” says Hutter. “The world just kind of stops.”