The Zion-Mount Carmel Highway is not just the road to somewhere else. Between the main canyon and the east entrance, SR-9 climbs switchbacks, passes through the long historic tunnel, and emerges into a landscape of pale slickrock domes and dry washes.
Oversized vehicles need tunnel control, and traffic can back up badly when the park is busy. Still, the drive is essential Zion, especially if you continue east toward Mount Carmel Junction and Kanab.