(CNN) — A river of cars greeted Marti Pawlikowski, of Lancaster, Pennsylvania, when she arrived at Zion National Park on a Road Scholar tour this spring. “It took us 45 minutes to get through,” she said, adding that the delays didn’t stop once she entered the Utah park. “Waiting in line for the shuttle in Zion reminded me of long lines in Disney World.” Last year, 26 national park sites saw record-breaking visitation. Now, many are in the thick of what looks like yet another blockbuster season.