M25 motorway Europe's second longest orbital road after the Berliner Ring, which is . Originally built almost wholly as a dual three-lane motorway, much of the motorway has been widened: to dual four lanes for almost half, to a dual five-lanes section between junctions 12 and 14 and a dual six-lane section between junctions 14 and 15. Further widening is in progress of minor sections with plans for managed motorways in many others. To the east of London the two ends of the M25 are joined to complete a loop by the non-motorway A282 Dartford Crossing of the River Thames between Thurrock
M25 motorway opened in 1986 traffic levels exceeded the maximum design capacity and in 1990 the Secretary of State for Transport announced plans to widen the whole of the M25 to four lanes. By 1993 the motorway, which was designed for a maximum of 88,000 vehicles per day, was carrying 200,000 vehicles per day. 15% of UK motorway traffic volume was on the M25 and there were plans to add six lanes to the section from Junctions 12 to 15 as well as widening the rest of the motorway to four lanes. In parts, particularly the western third this plan went ahead,