These medium black lines on a chart provide navigation to the arrival fix. What are they called?

The correct answer, Transition Routes, refers to specific paths on an aviation chart that guide aircraft from the en route phase of flight to the arrival fix for an airport. These routes help streamline the approach to landing by providing a predetermined path that pilots can follow, ensuring a more organized traffic flow and enhancing safety during the transition from high altitude to lower altitudes close to an airport. Transition routes are particularly beneficial in congested airspace where multiple flights may be approaching the same destination.

Airways, another option, are also established routes for aircraft, but they typically refer to medium-high altitude routes used during the en route phase of a flight, rather than directly to arrival fixes. Flight paths describe the actual trajectory that an aircraft follows; however, they are not defined by specific medium black lines on a chart. VOR radials provide navigation information based on a VOR (VHF Omnidirectional Range) station but do not constitute a defined route to an arriving fix. Thus, Transition Routes are the most appropriate descriptor for the medium black lines on the chart leading to an arrival fix.