The antonyms for the word "over pass" are "underpass" or "tunnel". An underpass is a road or passage that goes under a bridge or overpass. It is commonly used for pedestrians or smaller vehicles to cross under larger roads or railways. A tunnel, on the other hand, is a passage that goes through a mountain or under a body of water. It is often used for transportation means such as trains, cars, or subways. Unlike an overpass, both underpass and tunnel are considered safer alternatives for commuting, as they prevent accidents and provide a more controlled environment for people and vehicles to move.