What term describes key transportation routes that serve to distribute traffic in and out of the city?

The term that accurately describes key transportation routes serving to distribute traffic in and out of a city is "arterial roads." Arterial roads are major roads that handle larger traffic volumes and are designed to facilitate movement between different areas within urban environments. They connect different neighborhoods, commercial centers, and key locations, serving as primary pathways to manage the flow of vehicles efficiently.

While "radial roads" are also important as they extend from the center of the city outward like spokes on a wheel, they specifically address routes that radiate out from a central point. Their main function is to direct traffic toward the city center rather than focus on the distribution of traffic into and out of the city.

"Ring roads," on the other hand, provide routes that encircle a city, allowing traffic to bypass the city center and are not primarily concerned with distributing traffic into the central areas. Finally, "collector roads" serve a more localized function, helping to gather traffic from residential areas and direct it toward arterial roads but do not serve as the main highways for distributing traffic at a larger scale.

Thus, arterial roads best fit the description of key transportation routes integral to managing traffic flow into and out of urban centers.