What is an interchange?

An interchange is defined as a connection of a freeway to a road or another freeway via a series of ramps. This configuration allows vehicles to flow smoothly from one road or highway to another without the need for traffic signals, thereby facilitating efficient movement and reducing congestion. Interchanges often employ various designs, such as cloverleaf or diamond designs, to optimize traffic flow and safety, making them critical components of transportation networks.

Considering the other options, locations for gas stations and public transportation hubs are not interchanges but serve different purposes in transportation. A toll booth, meanwhile, is a specific structure related to road usage fees, typically found on toll roads, and does not represent the concept of connecting various roadways. Thus, the unique function of an interchange in connecting highways and roads through ramps is what makes it the correct answer.