The purpose of the track south of Drayton Park

[melikepie]

On a recent trip down the Northern City Line, I noticed a I think the term is a crossover (I'm probably wrong so please correct this) from the northbound track to the southbound track and judging by how shiny it looked, it seemed to be in regular use. It is immediately south of the station, in fact a northbound train was slightly on it. I guess it is mainly used for engineering works but can it be used for other purposes e.g. terminate all trains from Moorgate at Drayton Park for some reason?

[downdc]

This is reasoned speculation as opposed to an authoritative answer, but Drayton Park is where Northern City Line trains switch from DC to AC heading down/north and vice versa heading up/south. There is another crossover just north of the station, although not quite as close to the platforms. These two mean that a train which cannot switch to AC in platform 2 can head back south, and vice versa for a failure to switch to DC in platform 1. Turning services quite as short as that is very unusual one would imagine, but perhaps another service recovery possibility is the need to avoid the tunnels and return to the mainline, or perhaps avoid perturbation on the mainline, and remain in the segregated section! The two crossovers also allow for this.