Well it would be possible to run a shuttle service on the affected circle, say from Ibrox to Partick, due to the ramps taking trains to the surface (in pre modernisation days, this was not possible as cars were lifted from the tunnel), so trains can run to and from Ibrox to Partick, or further on, and then return other way. In doing so, when worknig wrong direction, they would need two drivers, and display a red lamp in the front window, as the trains are working non ATO on a normally ATO section of track in service.