The River Severn meanders past the town of Gloucester, widening to form the Severn estuary as it meets the sea. From Weston-super-Mare to Cardiff straight across is about 12 miles, but for a long time a road trip meant going via Gloucester, a distance of over 100 miles.
The first bridge, at a lower point than Gloucester, was the Sharpness rail bridge (now demolished) which opened in 1879. Soon after (1886) the rail system saw further improvement with a tunnel under the river.
But road users still had to go via Gloucester or use a car shuttle train service. A bridge had been proposed as early as 1824, when Thomas Telford was asked to advise on improvement to the mail coach service between London and Wales, but nothing was done then and the rail company opposed later plans. (A road bridge would reduce their profits.)
Eventually, as part of a national scheme of road improvements, a new bridge over the Severn was built, opening in 1966. It carries a motorway from Aust, Gloucestershire (where it replaced a ferry) to Chepstow, Wales, crossing both the Severn and the River Wye just upstream of their confluence. Click here for a map.
With only two lanes in each direction, it was soon clear that further capacity was needed. The Second Severn Crossing (later renamed the Prince of Wales Bridge) was opened in 1996 and this is now the lowest crossing point of the Severn, just downstream from the line of the rail tunnel.