Height Restrictions. Plan your route carefully. Many park roads feature historic bridges constructed with lower than conventional clearances. The shortest underpass on Park Loop Road is 11 feet 8 inches (3.56 m). Buses exceeding that height must exit Park Loop Road using Otter Cliff Road at Fabbri Picnic Area. If damage to a bridge overpass occurs, drivers will be cited and the park will seek restitution. Height restrictions are as follows: