In a recent study of the Texas Department of Transportation, Austin currently has the most congested road around the state with I-35 being the most congested of them all. The traffic in this specific road which is between State Highway 71 and US Highway 290 is notorious for its heavy traffic each year and number 1 in the 100 most congested roads in the state. Once in the road, traffic slows by up to 250% especially at rush hour traffic. Currently, the Transportation Department is considering adding new toll lanes in the area to improve the traffic situation in the I-35 route.
Read more about this here: Austin has the most congested road in Texas