The bridge carries the M4 motorway and is one of the main routes into South Wales . It was opened on 5 June 1996 to provide more traffic capacity than the original Severn Bridge , which opened in 1966 . The Second Severn Crossing is a bridge which carries the M4 motorway over the River Severn between England and Wales , inaugurated on 5 June 1996 by HRH The Prince of Wales to augment the traffic capacity of the original Severn Bridge built in 1966 .