Traffic volumes on Austin’s highways climbed after state employees were ordered back to the office full-time March 31, according to new data obtained by KUT News. But average travel speeds during morning and afternoon rush hours were little changed on Interstate 35, MoPac and U.S. Highway 183.

City streets showed even less fluctuation in travel times, aside from some construction zones.

Perhaps it shouldn’t be a surprise. Government employees make up less than 2% of the 1.5 million workers in the Austin-Round Rock-San Marcos metro area, according to the Bureau of Labor Statistics.

The mixed results also reflect a complicated reality: traffic congestion is shaped by overlapping forces — everything from crashes to signal timing — not just the number of vehicles on the road.

“When you start talking about traffic, there are lots of things in play besides what you’re thinking about,” said David Schrank, senior research scientist at the Texas A&M Transportation Institute. “We can look in generalities at what’s happening, but it’s very difficult to pinpoint.”

KUT News requested Texas Department of Transportation (TxDOT) data comparing the first week of the state’s return-to-office mandate with the first week of March to avoid muddying the numbers with the spring break slowdown.

The week of March 31, highway traffic volumes increased most on I-35 at Onion Creek Parkway. About 5% more cars and trucks traveled on weekdays in both directions, suggesting more people commuting from suburbs south of Austin.

But during the morning commute, defined as 6 to 10 a.m., average weekday travel speeds on I-35 at Onion Creek actually increased from 18 to 28 miles per hour. The afternoon commute saw a more predictable drop in southbound travel speeds from 28 to 25 miles per hour.

One factor could be that workers now have more flexibility to decide when they hit the road.

“They might take a call at the house before they leave,” Schrank said. “And then, ‘OK. I’m going to drive in now. Traffic sort of died down.’”

City traffic data — supplied by the traffic analytics company INRIX — shows little change on local streets.

That’s not to say certain pockets could be worse.

“I think the data doesn’t necessarily indicate where hotspots may be,” said Brian Craig with the city of Austin’s Transportation and Public Works Department. “So that is something that we are actively looking for.”

The city monitors intersections with cameras and adjusts traffic signal timing as needed, especially in areas where return-to-office orders might put more cars and trucks on the road.

One focus has been the TxDOT campus on Stassney Lane, where state employees returned to a site where they struggled to find parking.

“We’ve made [traffic signal] timing adjustments,” Craig said. “We know if we had not, it certainly would have become a very hot spot as far as congestion goes.”

Cesar Chavez Street to the west of I-35 was another trouble area. Construction at the Austin Convention Center slowed travel times by as much as 37%, but only during permitted working hours of 9 a.m. to 4 p.m.

One of Austin’s most reliably jammed roads didn’t change much. I-35 at Lady Bird Lake averaged about 10 miles per hour during the afternoon commute before the state’s return-to-office mandate.

The week after? Still 10 miles an hour.