The idea of a tunnel to allow traffic to cross the Thames was first suggested in 1924 for the Gravesend - Tilbury crossing. This was quickly changed to a crossing at Dartford and the first, western, tunnel was opened in 1960 (its construction being interrupted by the Second World War). It was intended to carry 2 million vehicles a year but by 1970 was carrying over eight million. Construction of the second, eastern, tunnel was completed in 1980 increasing the joint capacity of the two tunnels to 65,000 vehicles a day. Connection to the Essex M25 was completed in 1982 and the Kent side in 1986.