Which of the following best describes a divided highway?

A divided highway is characterized by having a physical separation between opposing lanes of traffic. This separation can take the form of a median, barrier, or other physical elements that distinctly divide the traffic traveling in opposite directions. This design enhances safety by reducing the likelihood of head-on collisions, as vehicles cannot easily cross over into oncoming traffic.

While the first option mentions having multiple lanes, it does not necessarily imply that traffic is separated; two lanes in one direction could still be a part of an undivided highway. The third choice suggests that pedestrian and vehicle use is allowed, which is more typical of roads designed for mixed use rather than tailored specifically as divided highways. Lastly, the fourth option describes a one-lane road with no markings, which fundamentally lacks the characteristics of a divided roadway altogether. Thus, the defining element of a divided highway is indeed the physical separation that enhances safety and traffic flow.