Non-revenue track

Non-revenue track, or a non-revenue route, is a section of track or transport route that is not used to carry revenue-earning freight or goods nor for scheduled passenger services. The term is used to refer mainly to sections of track or routes in public transport systems, such as rapid transit and tramway networks, but non-revenue track or routes can also be found in other transport systems. Non-revenue tracks may be used for revenue service during temporary reroutings.

This keyword could refer to multiple things. Here are some suggestions: