Which of the following are the four principal types of interstate interchanges?

The four principal types of interstate interchanges are Directional, Clover Leaf, Diamond, and Trumpet. Each of these interchange types is designed to facilitate the efficient movement of traffic between highways while minimizing congestion and enhancing safety.

A Directional interchange allows for smooth transitions between highways, ensuring vehicles can move in the intended direction without stopping. Cloverleaf interchanges are designed with looping ramps that allow vehicles to enter and exit highways without having to stop at traffic signals. Diamond interchanges are characterized by their simple design, which accommodates traffic flows with minimal space requirements, creating a direct connection between a primary road and a secondary road. Lastly, the Trumpet interchange is used when one roadway terminates at another, ideal for connecting a freeway with a less significant road.

The other choices do not represent standard classifications of interstate interchanges. One-way and two-way intersections refer more to traffic flow direction rather than interchange design. Split, merge, diverge, and circle refer to various traffic flow concepts rather than specific interchange types. Roundabout, turnabout, U-turn, and intersection describe different traffic patterns and designs but do not pinpoint the main types of interchanges seen on interstate systems.