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 of London, part of the London Orbital. The combined motorway was given the designation M25 which had originally been intended for the southern and western part of Ringway 4 and the M16 designation was dropped. The section of Ringway 3 west of South Mimms anti-clockwise around London to Swanley in Kent was cancelled. The stages were not constructed contiguously but in small sections. As the orbital road developed the sections were linked. Each section was presented to planning authorities in its own right and was individually justified, with almost 40 public inquiries relating to sections of the route. Maps at