What is defined as a divided, controlled access highway for through traffic?

The correct choice, which defines a divided, controlled access highway for through traffic, is a freeway. A freeway is designed primarily for high-speed vehicular traffic, allowing for uninterrupted flow by minimizing intersections and utilizing overpasses, underpasses, and ramps. This design ensures that vehicles can travel long distances without the interruptions that occur on other types of roads, such as those with stoplights or pedestrian crossings.

By having controlled access, freeways limit entry and exit points, providing safety and efficiency in travel, which is essential for maintaining high speeds and facilitating long-distance travel. The separation of traffic flow helps to manage the risks associated with high-speed driving, reducing the potential for accidents.

In contrast, other roadway types, such as expressways, may allow for traffic control devices that could interrupt flow or have at-grade intersections. Side roads primarily cater to local traffic and are not designed for through traffic at high speeds. Interstates are a specific category of freeways that form part of the National System of Interstate and Defense Highways; while they share many characteristics with freeways, the general term "freeway" encompasses a broader range of road types.