The coping is supported by 42 segmental deck arches (21 on each side) that span the tops of 22 transverse walls beyond the longitudinal walls. The longitudinal walls are five feet thick with a four-foot gap between them joined with occasional tie stones. More construction details are available in the original . When the viaduct had a single set of tracks, the rails were placed directly over the longitudinal walls as the cavity's width is less than standard gauge. When the viaduct was double tracked in 1860, the inside rails were placed directly over the longitudinal walls and the outside rails were supported by the deck arches.