The first motorway suspension bridge was inaugurated on 8 September 1966, and the newer cable-stayed bridge, a few miles to the south, was inaugurated on 5 June 1996. The Second Severn Crossing marks the upper limit of the Severn Estuary.
The two Severn crossings are regarded as the main crossing points from England into South Wales. Prior to 1966 road traffic between the southern counties of Wales and the southern counties of England either had to travel via Gloucester or take the Aust Ferry, which ran roughly along the line of the Severn Bridge, from Old Passage near Aust to Beachley. The ferry ramps at Old Passage and Beachley are still visible.
Tolls are collected on both crossings from vehicles travelling in a westward direction only. As of January 2012, the toll for small vehicles is £6.00.
Text from Wikipedia
Having lived in the shadows of the M48 Severn Bridge for so many years, it becomes taken for granted just what a stunning piece of engineering genius it really is.