For 360 days each year, Manchester, Tennessee is a quiet town of 10,000 people. It has not quite 50 churches, eight schools, and three supermarkets. But for several days each June, it balloons into the seventh largest city in the state as 80,000 people and perhaps half that many cars descend on the outskirts for the Bonnaroo Music and Arts Festival. Music is the focus (Pearl Jam! J. Cole! Ellie Goulding!), but the vehicles are an inescapable sideshow.

The first festival, in 2002, caught the state Department of Transportation and Highway Patrol completely unaware. "It was quite a nightmare," says Jennifer Flynn, a DOT community relations manager. "Traffic was backed up for miles and miles and miles." Today, festival organizers work with the city, the county, the state and a conference roomful of consultants to create a plan for getting everyone in and out quickly and efficiently.

You can't beat congestion—try squeezing thousands upon thousands of vehicles through the back roads of Appalachia. But the effort to manage traffic and keep people moving started months before the festival kicks off Wednesday.

Keep 'Em Moving

The first thing the traffic team does is confine congestion to crowds, and the roads they're most likely to use. A week before the show starts, state officials and the local news tell everyone who isn't attending the festival to stay the hell away—especially big-rigs and buses. Festival organizers send everyone with a ticket personalized directions providing the fastest way of getting there.

The day before the concerts begin, state officials descend on Interstate 24, outside of town, limiting the left lane to through traffic and locals while everyone headed to the venue creeeeeeps along in the right lane and on the shoulder.

Put It Up, Knock It Down

Like youth and the festival itself, Bonnaroo's traffic infrastructure is ephemeral. The DOT drags in temporary signs that line the roads leading to Manchester to send updates and helpful messages like “RAMP CLOSED” to everyone slogging toward town. Even Bonnaroo’s main exit off the highway lasts only a little longer than cotton candy. For most of the year, it's a closed gate.

The festival’s three entry checkpoints are icons of 'Rooian crowd control, and sit at the dark heart of its congestion. Every car, no exceptions, must stop so it and its occupants can be checked for camping passes and wristbands, contraband (no weapons, drones, drugs, or kegs) and to answer the inevitable questions before directing music fans to the right parking lot, er, field. Analyzing "years of data" makes things go relatively quickly, says Jeff Cuellar, who helps organize the festival for AC Entertainment. But his team is always looking for ways to make things go even more smoothly.

Stay Flexible

No matter how solid your plan, something always goes sideways. It's inevitable, and explains why the DOT always has a "rapid response team" of 30 people standing by to fix flats, deliver gas, and haul broken-down hoopties off the highway. Roughly 110 troopers will be there, too, doing what they do. They'll all have radios, with everyone on the same wavelength, literally and figuratively. Cuellar says “traffic is this living, breathing thing.” Taming it requires constant communication.

Nix the Personal Car

As always, the best way to mitigate congestion is to avoid it. And that means ditching cars. The festival encourages carpooling, and there are websites and online forums to help folks find a ride. A few Greyhound buses roll into Manchester each day, and festival-sponsored shuttles bringing people in from the airport in Nashville. And this year, Bonnaroo is getting into ridesharing, working with Skedaddle to arrange convoys of vans and buses. Because if you’re going to be in pop-up Tennessee traffic, you might as well be with a driver and ten of your closest friends.