"Rural highways" refers to roads that are located in or pass through rural areas, which are sparsely populated areas outside of cities. Full definition
The nearby rural highways are popular destinations for road biking, as well. (health.com)
Drowsy driving accidents are the most common on rural highways with little to no nighttime lighting and high speed limits, and they often involve vehicles colliding with each other head - on. (newmexicoinjury.com)
In my drive loop in an SE model, the computer reported 53 mpg on mostly rural highways. (hybridcars.com)