Springdale sits at the western entrance to Zion National Park on Highway 9, three hours' drive from Las Vegas and four and a half from Salt Lake City. The closest commercial airports are St George (45 minutes) and Cedar City (an hour and a quarter); both have several daily flights from Salt Lake. Las Vegas is the cheapest air gateway and most international visitors use it.
Within Springdale, a free town shuttle runs the length of the main street from spring through autumn and connects to the park entrance shuttle inside Zion. From late February to late November, private vehicles are not permitted up the canyon road; you ride the park shuttle, which is free, frequent, and the only way to see the main canyon. Outside those months you can drive your own car all the way up.
The Mount Carmel Tunnel on Highway 9 connects Zion to Bryce Canyon and the Grand Staircase region beyond; allow at least an hour and a half for the drive. Vehicles over 11 feet 4 inches tall or 7 feet 10 inches wide need a one-way escort permit through the tunnel.