ABOVE THE GROUND the extension involved the building of a viaduct to carry the line across the North Circular Road between Bounds Green and Southgate. The viaduct is built entirely of brick, with brick piers and rounded arches. The arches were built over timber falsework, as seen in this photograph.
A photograph of the works on the site of Turnpike Lane Station. The curved subway, with a lining of cast-iron segments, is one of the subways by which passengers gain access to the station underground. Escalators were installed in accordance with modern practice. The vertical shaft seen in the photograph was not intended for a lift but was sunk to give communication with the tube tunnel during construction.
RISING TO THE SURFACE, the railway emerges from the twin tube tunnels through the brickwork portals, as shown in this photograph. The gradient is continued through an excavated trench or cutting until surface level is reached. The line then proceeds as a normal double-track electric railway, running in cuttings or on embankments, bridges or viaducts.