Humber Bridge single-span suspension bridge for 16 years from its opening in July 1981, until the opening of the Great Belt Bridge in June 1997, and was relegated to third place with the opening of the Akashi Kaikyō Bridge in April 1998. It is now the eighth longest single-span suspension bridge. The central span, at 1410 m (4640 ft), is the UK's longest. It remains the longest single-span suspension bridge in the world that one can cross on foot or by bicycle. The bridge is crossed twice during the annual Humber Bridge half marathon. In July 2013, work began on introducing a
Suspension bridge deck is added). One can see the shape from the constant increase of the gradient of the cable with linear (deck) distance, this increase in gradient at each connection with the deck providing a net upward support force. Combined with the relatively simple constraints placed upon the actual deck, this makes the suspension bridge much simpler to design and analyze than a cable-stayed bridge, where the deck is in compression. In an underspanned suspension bridge, the main cables hang entirely below the bridge deck, but are still anchored into the ground in a similar way to the conventional type. Very