Interstate 15, the main corridor through southwestern Utah, connects St. George and Cedar City with Las Vegas and Salt Lake City and also intersects with Interstate 70 about 75 miles north of Cedar City. It's actually quite pretty for an interstate, but the scenery becomes even more dramatic as you venture onto the region's main two-lane highways, such as Highway 9 through Springdale and Zion National Park, Highways 14 and 143 through Brian Head and Dixie National Forest, U.S. 89 through Paria Canyon, Kanab, and Panguitch, and Highway 12 through Bryce City, Tropic, Escalante, and Torrey. If you travel between I–15 and U.S. 89 via Highway 9, you must pay the $35 admission fee to Zion National Park even if you do not plan to stop and visit. If you're planning to visit Zion and at least two other parks, however, you should think about buying an Interagency Annual Pass for $80.
In winter, Highway 143—the primary access road to Brian Head and Cedar Breaks National Monument—occasionally closes when there's heavy snowfall, and Highway 148 shuts down all winter, typically from mid-November through February. Utah Department of Transportation provides free, up-to-the-minute interactive road conditions. You can also download the app or check conditions online (udottraffic.utah.gov).
Keep in mind that services are few and far between on back roads in this part of the state, especially as you head east from the Interstate 15 corridor. Cell service can be spotty in these areas, too. It's best to download maps and top off your gas tank before you set out to explore these areas.