Central Oregon’s population is swelling with people as thousands of visitors arrive for the total solar eclipse, and Prineville has seen the brunt of the congestion.

People traveling east along U.S. Highway 26 through the Crook County city on their way to Symbiosis, the 30,000-person festival at Big Summit Prairie, have filled Prineville to capacity.

Heavy traffic prompted the closure of Highway 26 to eastbound travel Thursday afternoon, according to the Oregon Department of Transportation.

The highway was reopened Thursday night.

Traffic between the city and the site of Symbiosis backed up as much as 14 miles Wednesday — and slightly less Thursday, at 12 miles.

Vicky Ryan, emergency preparedness coordinator for Crook County, said there had been reports of people sitting in cars for three hours between Prineville Reservoir and Big Summit Prairie.

“It seems to be coming in waves,” Ryan said of the traffic.

ODOT altered the traffic flow through Prineville to keep traffic moving to Big Summit Prairie.

At around 10:45 a.m. Wednesday, transportation officials altered traffic lights along Third Street through downtown Prineville, setting them to favor east-west traffic. Ryan said the new setup would make it more difficult for north-south drivers to turn left onto the main road, and recommended that people attempting to do so find alternate routes.

However, Peter Murphy, state transportation spokesman, said the setup will give east-west traffic an easier path through the city.

“It really is a balancing act, and right now, that balance has shifted toward Symbiosis,” Murphy said.

When they closed the highway Thursday afternoon, Murphy said, officials had a police car stationed at the intersection to divert traffic onto state Highway 380.

Festival attendees could get to Big Summit Prairie off the route using Forest Service roads. Murphy added that guides were stationed along the road to ensure visitors didn’t get lost.

The eclipse is expected to bring about 200,000 people to Central Oregon by Monday morning. Of that total, at least 30,000 are expected at Symbiosis, which began Thursday. Ryan said fewer than half of the attendees had made it through Prineville so far, and she is expecting traffic to stay severe east of Prineville into Friday.

“We’re expecting the majority of the traffic to be through by tomorrow afternoon,” Ryan said Thursday.

Once people get settled at Symbiosis, Ryan said she expects traffic through town to die down somewhat, at least until people travel back through Prineville once the festival ends on Wednesday.

However, Murphy said the stretch of Highway 26 was the only real problem area, as of Thursday afternoon. While the trip along Highway 126 between Redmond and Prineville, which normally takes around 20 minutes, more than doubled on Wednesday afternoon, Murphy said the average trip time had not exceeded 25 minutes between the two cities on Thursday.

“It’s running pretty close to normal,” Murphy said of that stretch of road.

Madras is expected to become the unofficial center of eclipse festivities once Oregon SolarFest kicks off on Friday. However, Murphy said U.S. Highway 97 between Bend and Madras had not yet become congested.

“That’s all green,” Murphy said Thursday afternoon.

He added that he had not heard about any significant traffic accidents along the highways.

For live updates on road conditions, ODOT encourages travelers to keep tabs on www.tripcheck.com.

—Reporter: 541-617-7818, shamway@bendbulletin.com