The former Throstle Nest Bridge, now the Arnold Road Subway

The former Throstle Nest Bridge, now known as the Arnold Road Subway, is a former railway accommodation underbridge designed by George Stephenson for the Stockton & Darlington Railway in 1824. It was widened in 1830 and again in the late 19th century. Since 2008, it has served as a pedestrian subway beneath the B6279 road.

The bridge is constructed from ashlar sandstone and cream-coloured machine-made brick. Both the north and south sides of the bridge are nearly identical, featuring plain ashlar spandrels and curving wing-walls topped with flat coping slabs. The arch is semi-circular and made up of four rings of brickwork, which form the barrel vault from the late 19th-century widening. The original bridge and the 1830 widening have stone ashlar barrel vaults that match the dimensions of the later extensions, and the butt-joints between the widenings are clearly visible.