What is the main distinction between a highway and a freeway/expressway?

The primary distinction that makes freeways and expressways unique compared to highways is the absence of traffic lights. Freeways and expressways are designed for high-speed travel without interruptions caused by stop signs, traffic lights, or direct intersections. This design allows for smoother flow of traffic, which is essential for maintaining higher speeds and minimizing the chances of accidents.

On the other hand, highways often intersect with local roads, which may include traffic signals and stop signs, affecting the overall speed and flow of vehicles. This designed separation on freeways and expressways not only facilitates faster travel times but also enhances safety by reducing the potential for collisions that can occur at intersections.

While the other options contain elements that may be true in specific contexts, they do not capture the primary difference that defines the functionality and safety rationale behind the design of freeways and expressways compared to highways.