If you're planning on traveling to view the rare total eclipse over the U.S. on Aug. 21, brace yourself for company.

The U.S. Department of Transportation is warning state and local departments within the the narrow, 70-mile-wide band of totality to prepare for an onslaught of commuters eager to witness the phenomenon. While much of the United States will experience some measure of the eclipse, 14 states will have a front-row seat as the moon's shadow crosses from Oregon to South Carolina. For an event that's being called "once-in-a-lifetime," chances are good that a portion of the more than 200 million people within a day's drive of the path of totality will decide to hit the road.

"The problem is that these millions of Americans will produce predictable traffic congestion," writes eclipse cartographer Michael Zeiler. "Imagine 20 Woodstock festivals occurring simultaneously across the nation. Large numbers of visitors will overwhelm lodging and other resources in the path of totality. There is a real danger during the two minutes of totality that traffic still on the road will pull over at unsafe locations with distracted drivers behind them."

The U.S. DOT is advising municipalities to treat the eclipse as a "planned special event" for which there is no recent precedent in American history. Indeed, the last time a total solar eclipse traversed the U.S. in 1918, car registrations numbered only a little over 5.5 million. Today, that number stands at north of 263 million.

According to GreatAmericanEclipse.com, South Carolina may bear the brunt of eclipse commuters on August 21st. According to GreatAmericanEclipse.com, South Carolina may bear the brunt of eclipse commuters on Aug. 21. (Photo: GreatAmericanEclipse.com)

"Travelers should be at their observation location a minimum of a couple hours before totality," the U.S. DOT advises in its eclipse fact sheet. "The role of state and local DOTs may include instituting roadblocks or other measures to keep people from making illegal turns as they drive around looking for 'the perfect spot' as eclipse totality nears."

Depending on weather conditions, an in-depth analysis conducted by Zeiler found that anywhere from 1.85 and 7.4 million people will visit the path of totality on eclipse day. In fact, one crafty geomapper decided to plot that out, producing and sharing this helpful Google map:

The U.S. DOT is urging those states within the path of totality to share their experiences in handling the traffic surge with those in the bullseye for the next total solar eclipse to cross the nation on April 8, 2024.

Curious to see how the eclipse might look from your location to weigh your options? Check out the details on Google's helpful online simulation here.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.